Consumer Theory

An indifference curve (IC) is the locus of combinations of two goods that give the consumer the same level of satisfaction; the consumer is "indifferent" among all bundles on a single IC. The higher an IC, the greater the utility it represents (assuming "more is better").
Assumptions: Rational consumer; monotonic preferences (non-satiation); goods are divisible; and ordinal utility.
Salient features: (1) Downward sloping: To keep utility constant, an increase in one good must be offset by a decrease in the other (negative slope). (2) Convex to the origin: Diminishing Marginal Rate of Substitution (MRS) — as the consumer substitutes good for , the amount of they are willing to give up per extra unit of falls. (3) Do not intersect: If two ICs crossed, it would violate transitivity and monotonicity (same bundle giving two different utility levels). (4) Higher ICs show higher satisfaction: Bundles on a higher curve have more of at least one good and not less of the other. (5) ICs are dense: Between any two ICs, there exists another IC, reflecting continuity of preferences. (6) MRS equals IC's (absolute) slope: , which typically diminishes along the curve.
Diagram (verbal): On a two-good plane ( on horizontal, on vertical), draw a family of smooth, downward-sloping, convex curves with farthest from the origin. The slope at any point equals the MRS.
Use: Together with the budget line, ICs determine consumer equilibrium where at the tangency point.
Limitations: Ignores income effects across widely separated ICs; assumes stable preferences and continuous divisibility, which may not always hold.

Idea: Total Utility (TU) is the cumulative satisfaction from all units consumed; Marginal Utility (MU) is the additional satisfaction from the last unit: . As more units are consumed, MU generally diminishes. When MU is positive, TU rises; when MU falls to zero, TU reaches its maximum; when MU becomes negative, TU declines.
Example (table):
Quantity: 1,\;2,\;3,\;4,\;5,\;6
TU: \;10,\;18,\;24,\;28,\;30,\;29
MU: \;10,\;8,\;6,\;4,\;2,\;-1
Here MU shrinks with each unit; at the 5th unit MU and TU peaks at ; the 6th unit yields MU , so TU falls.
Diagram (verbal): The TU curve starts from the origin, increases at a diminishing rate, becomes flat at its peak (where MU curve cuts the quantity axis at MU ), and then bends downward if consumption continues. The MU curve slopes downward, crossing zero at TU's maximum.

A budget line shows all bundles of two goods a consumer can buy given money income and prices. Algebraically: , with slope , -intercept and -intercept . Points on the line are affordable with full income spent; inside are affordable with savings; outside are unaffordable.
Example: If income , (pens) and (notebooks), intercepts are pens and notebooks. Any combination on the straight line between and is just affordable; e.g., satisfies .
Diagram (verbal): Plot pens on the -axis and notebooks on the -axis; draw a straight downward line joining and . A rise in income shifts the line parallel outward; a fall in income shifts it inward. A price change pivots the line around the other intercept.

Concept: Total utility (TU) is the sum of satisfaction from all units consumed, while marginal utility (MU) is the increment: .
Law: As consumption of a good rises, MU typically falls after a point (diminishing MU) due to saturation of wants.
Implications: Consumers allocate income so that the ratio of MU to price is equalized across goods (utility maximization rule). When TU is maximum, MU becomes zero; if further units reduce satisfaction, MU turns negative and TU falls.
Use: MU underpins downward-sloping demand and the idea of consumer equilibrium.

Consumer equilibrium is achieved when the budget line is tangent to the highest attainable indifference curve. This point represents the optimal combination of two goods that maximizes a consumer's satisfaction given their budget constraints.
(Include a diagram showing the budget line and indifference curves.)

An indifference curve map consists of multiple indifference curves showing different levels of utility. Each curve represents combinations of two goods that provide the same level of satisfaction to a consumer. The map demonstrates the concept of higher utility with curves further away from the origin.
(Provide a labeled diagram with indifference curves in your answer book.)

Price Elasticity of Demand (PED) measures the responsiveness of the quantity demanded of a good or service to a change in its price. In other words, it reflects how much the quantity demanded changes when there is a change in the price of the good. The formula to calculate PED is: Where: - is the percentage change in quantity demanded, - is the percentage change in price. When PED is greater than 1, demand is said to be elastic, meaning that consumers respond strongly to price changes. If PED is less than 1, demand is inelastic, meaning that consumers do not significantly change their buying behavior in response to price fluctuations. When PED is exactly 1, the demand is unitary elastic, indicating that the percentage change in quantity demanded is equal to the percentage change in price. Factors Affecting Price Elasticity of Demand:
1. Availability of Substitutes: - When there are close substitutes available for a product, the demand for the product tends to be more elastic. If the price of a product rises, consumers can easily switch to substitutes. For example, if the price of tea increases, consumers may switch to coffee, making the demand for tea more elastic. 2. Necessity vs. Luxury: - Necessities tend to have inelastic demand, as consumers cannot easily do without them. For example, basic healthcare or essential food items often have inelastic demand because people need them regardless of price changes. In contrast, luxury goods (such as high-end electronics or expensive cars) tend to have elastic demand because people can forgo or delay purchasing them if prices rise. 3. Proportion of Income Spent on the Good: - Goods that account for a large portion of a consumer's income typically have more elastic demand. This is because any increase in price will significantly impact the consumer's budget, leading to a greater reduction in quantity demanded. For instance, if the price of a car increases significantly, it will lead to a larger decrease in demand compared to a minor increase in the price of a candy bar. 4. Time Period: - The price elasticity of demand can vary depending on the time frame considered. In the short run, demand is often more inelastic because consumers may not immediately find substitutes or adjust their consumption habits. However, in the long run, demand tends to become more elastic as consumers have more time to adjust their behavior, find alternatives, or switch to different products. For example, if the price of gasoline rises, consumers may initially not change their consumption, but over time, they may buy more fuel-efficient cars or use alternative transport. 5. Definition of the Market: - The broader the definition of a good, the more inelastic its demand tends to be. For instance, the demand for "food" in general is likely to be more inelastic than the demand for a specific food item like "organic avocados." Specific goods with more narrow definitions typically have more elastic demand because consumers can easily switch to alternatives within that category. 6. Brand Loyalty: - If consumers are highly loyal to a brand, the demand for that brand's products will be less elastic. Even if the price of a brand increases, loyal customers may continue purchasing it. For instance, Apple products often exhibit inelastic demand due to strong brand loyalty among its consumers. Implications of PED: - Elastic Demand: If demand is elastic, businesses might lower prices to increase sales and total revenue, as the percentage increase in quantity demanded will offset the price decrease. - Inelastic Demand: If demand is inelastic, businesses can raise prices to increase total revenue since the decrease in quantity demanded will be proportionally smaller than the price increase. Understanding the factors that affect price elasticity helps businesses and policymakers make informed decisions about pricing, tax policies, and subsidies.

Elasticity of Demand (also known as Price Elasticity of Demand, PED) measures the responsiveness of quantity demanded to a change in the price of a good or service. It indicates how much the quantity demanded will change when there is a change in the price of the product. If the demand is highly responsive to price changes, it is said to be elastic, whereas if it is less responsive, it is inelastic. The formula to calculate elasticity of demand is: Where: - is the percentage change in quantity demanded, - is the percentage change in price. Elasticity can be classified into three categories based on the value of PED:
1. Elastic Demand: If , demand is elastic. A small change in price leads to a large change in quantity demanded. Luxury goods and goods with close substitutes tend to have elastic demand. 2. Inelastic Demand: If , demand is inelastic. A change in price has a relatively small effect on the quantity demanded. Necessities such as salt or water tend to have inelastic demand. 3. Unitary Elasticity: If , demand is unitary elastic, meaning the percentage change in quantity demanded is equal to the percentage change in price. Methods of Measuring Elasticity of Demand: There are several methods to measure the price elasticity of demand:
1. Percentage Method: This method calculates the percentage change in quantity demanded relative to the percentage change in price. The formula is: 2. Total Expenditure (Revenue) Method: This method examines the relationship between total revenue (TR) and price. If the price increases and total revenue decreases, the demand is elastic. If the price increases and total revenue increases, the demand is inelastic. If total revenue remains constant when price changes, the demand is unitary elastic. 3. Point Method: The point method is used when the change in price is very small. It calculates elasticity at a specific point on the demand curve using the slope of the demand curve. The formula is: Where is the price, is the quantity, and is the slope of the demand curve. 4. Arc Method: The arc method is used when the price change is large. It calculates elasticity using average values of price and quantity over the range of the price change. The formula is: Where and are the average quantities and prices before and after the price change. These methods help businesses, policymakers, and economists analyze consumer behavior and set optimal pricing strategies.

An Indifference Curve is a graph representing various combinations of two goods that provide the same level of satisfaction or utility to the consumer. In other words, any point on the indifference curve gives the consumer the same level of happiness or utility. Indifference curves are used in consumer theory to analyze consumer preferences and choices between different bundles of goods. Each curve represents a different level of satisfaction, so higher indifference curves (further from the origin) represent higher levels of utility, and lower indifference curves represent lower levels of utility. Characteristics of Indifference Curves:
1. Downward Sloping: Indifference curves are typically downward sloping, reflecting the trade-off between two goods. As a consumer increases the quantity of one good, they must decrease the quantity of the other good to maintain the same level of satisfaction. 2. Convex to the Origin: Indifference curves are convex to the origin, meaning that the slope of the curve becomes flatter as one moves from left to right. This reflects the principle of diminishing marginal rate of substitution (MRS), which states that as a consumer substitutes one good for another, they are willing to give up fewer units of the good being lost for each additional unit of the good being gained. 3. Non-Intersecting: Indifference curves cannot intersect each other. If two curves were to intersect, it would imply that the same bundle of goods provides two different levels of satisfaction, which is logically inconsistent. 4. Higher Curves Represent Higher Utility: Curves further from the origin represent higher levels of satisfaction. A consumer prefers a combination of goods that lies on a higher indifference curve as it provides more utility. 5. Indifference Curves are Smooth: Indifference curves are typically smooth and continuous. This implies that consumers can make smooth trade-offs between goods, and there are no sudden jumps in utility. 6. Indifference Curves are Continuous: Consumers are assumed to have continuous preferences, meaning they can compare and rank every possible combination of goods. This implies that between any two points on an indifference curve, there are an infinite number of points that provide the same level of satisfaction. 7. Marginal Rate of Substitution (MRS): The slope of the indifference curve at any point is called the marginal rate of substitution (MRS), which represents the rate at which a consumer is willing to exchange one good for another while keeping their level of satisfaction constant. The MRS diminishes as more units of one good are substituted for the other, which reflects diminishing marginal utility. Example: For example, consider two goods: apples and bananas. If a consumer is indifferent between having 5 apples and 3 bananas or 4 apples and 4 bananas, these combinations would lie on the same indifference curve, meaning both provide the same level of utility to the consumer. Importance of Indifference Curves: Indifference curves help explain consumer behavior and choices under the assumption that consumers have well-defined preferences. By analyzing the curves, economists can determine how changes in income, prices, and preferences influence consumer choices and demand.

Total Utility refers to the total satisfaction or pleasure derived from consuming a given quantity of goods or services. It is the sum of marginal utilities of each additional unit consumed. As consumption increases, total utility increases, but at a diminishing rate due to the law of diminishing marginal utility. The concept helps explain consumer behavior and how choices are made to maximize satisfaction. It plays a central role in understanding demand in microeconomics.

The slope of the indifference curve is negative, reflecting the trade-off between two goods that a consumer is willing to make. As the quantity of one good increases, the quantity of the other good must decrease in order to maintain the same level of utility.

A market demand curve shows the relationship between the price of a good and the quantity demanded by all consumers in the market at different prices.

The Law of Equimarginal Utility states that a consumer will allocate their income in such a way that the marginal utility (MU) derived from each good or service purchased is equal, given the prices of those goods. In simpler terms, consumers maximize their total utility by spending their money in a way that the last unit of currency spent on each good provides the same level of marginal utility. - Consumer Equilibrium: The consumer reaches equilibrium when the ratio of the marginal utility to price is equal for all goods. This condition can be mathematically expressed as: Where are the marginal utilities of goods , and are their respective prices. This means that the consumer will distribute their budget so that the marginal utility per rupee spent on each good is equal across all goods.

- Cardinal Utility: Measures utility in numerical terms (e.g., utils) and assumes that the consumer can quantify satisfaction. - Ordinal Utility: Measures utility in terms of preference ranking, where the consumer ranks goods in order of preference without assigning numerical values.

- Substitute Goods: Goods that can replace each other, such as tea and coffee. - Complementary Goods: Goods that are used together, such as printers and ink cartridges.

The law of diminishing marginal utility states that as a person consumes more units of a good, the additional satisfaction (marginal utility) derived from each additional unit decreases.

Price Elasticity of Demand measures the responsiveness of quantity demanded to changes in the price of a good or service. It is expressed as:

The consumer is in equilibrium when the Marginal Rate of Substitution (MRS) between two goods and is equal to the ratio of their prices, i.e., . This ensures that the consumer is maximizing utility given their budget constraint.

Contraction of demand refers to a decrease in quantity demanded due to a price increase, as per the law of demand.

Marginal utility refers to the additional utility derived from consuming one more unit of a commodity. When total utility reaches its maximum, marginal utility becomes zero because there is no additional satisfaction obtained from consuming extra units.

In basic economics, desire is the mere willingness or wish to have a commodity.
A want is a broader term for human needs/wishes and may be non-specific.
Demand is an effective desire: desire backed by the ability and willingness to pay at a given price and time.
Since the question mentions only the willingness to obtain (without ability to pay), it corresponds to desire, not demand.

Marginal utility refers to the additional satisfaction or utility derived from consuming one more unit of a good or service.

Step 1: Understanding the Concept:
Consumer's Equilibrium refers to a situation where a consumer, with their given income and market prices, spends their money on goods and services in such a way that they get the maximum possible satisfaction (utility). At this point, they have no incentive to change their consumption pattern. Utility analysis, also known as Cardinal Utility Analysis, assumes that utility can be measured in cardinal numbers (utils).

Step 2: Equilibrium in Case of a Single Commodity:
A consumer purchasing a single commodity will be at equilibrium when the marginal utility of the commodity in terms of money is equal to its price. The condition is: Where: \begin{itemize} \item is the Marginal Utility of good X. \item is the Price of good X. \item is the Marginal Utility of Money (the utility of one rupee, assumed to be constant). \end{itemize} If , the consumer will buy more of X. If , they will buy less. Equilibrium is reached only when they are equal.

Step 3: Equilibrium in Case of Two or More Commodities (Law of Equi-Marginal Utility):
When a consumer is buying two or more commodities, the equilibrium condition is that the ratio of the marginal utility to the price must be the same for all commodities consumed. This is known as the Law of Equi-Marginal Utility or Gossen's Second Law. The condition for two goods, X and Y, is: This means that the consumer gets the same marginal utility from the last rupee spent on each good. If the ratio is higher for good X than for good Y, the consumer will shift expenditure from Y to X until the ratios become equal.

Step 4: Final Answer:
Consumer's equilibrium under utility analysis is achieved when the marginal utility per rupee spent is equal for all goods purchased and is also equal to the marginal utility of money. This ensures that the consumer is maximizing their total satisfaction.
Solution (Calculation of Elasticity of Demand):

Step 1: Understanding the Concept and Formula:
The question asks to calculate the Price Elasticity of Demand ( ). The percentage method is the most appropriate here. The formula is: Where: \begin{itemize} \item P = Initial Price \item Q = Initial Quantity \item = Change in Price ( ) \item = Change in Quantity ( ) \end{itemize}

Step 2: Identifying the Given Values:
\begin{itemize} \item Initial Price (P) = ₹ 5 \item New Price ( ) = ₹ 4 \item Initial Quantity (Q) = 100 units \item New Quantity ( ) = 110 units \end{itemize}

Step 3: Calculating the Changes:
\begin{itemize} \item Change in Price ( ) = \item Change in Quantity ( ) = \end{itemize}

Step 4: Substituting the Values into the Formula and Calculating:
Step 5: Final Answer and Interpretation:
The price elasticity of demand is 0.5.
Since , the demand is inelastic. This means that the percentage change in quantity demanded (10%) is less than the percentage change in price (20%).

Step 1: Understanding the Concept:
The relationship between the price of a commodity and the quantity demanded is explained by the Law of Demand. The law states that, other things being equal (ceteris paribus), the quantity demanded of a commodity is inversely related to its price.
This means: \begin{itemize} \item When the price of a commodity falls, its quantity demanded rises. \item When the price of a commodity rises, its quantity demanded falls. \end{itemize}

Step 2: Detailed Explanation:
This inverse relationship occurs due to two main effects: \begin{enumerate} \item Income Effect: When the price of a commodity falls, the real income (or purchasing power) of the consumer increases. They can now buy more of the same commodity with the same amount of money. \item Substitution Effect: When the price of a commodity falls, it becomes relatively cheaper compared to its substitutes. Consumers will therefore substitute this cheaper good for other, now relatively more expensive, goods. \end{enumerate} The combined result of the income and substitution effects is that a lower price leads to a higher quantity demanded, and vice versa.

Step 3: Explanation with Diagram:
The relationship is represented by a downward-sloping demand curve. \begin{center} \begin{tikzpicture} \draw[->] (0,0) -- (6,0) node[right] {Quantity Demanded}; \draw[->] (0,0) -- (0,5) node[above] {Price}; \draw[thick, color=blue] (1,4) -- (4,1) node[right] {DD (Demand Curve)}; \draw[dashed] (1.5, 3.5) -- (1.5, 0) node[below] { }; \draw[dashed] (1.5, 3.5) -- (0, 3.5) node[left] { }; \draw[dashed] (3.5, 1.5) -- (3.5, 0) node[below] { }; \draw[dashed] (3.5, 1.5) -- (0, 1.5) node[left] { }; \fill (1.5, 3.5) circle (2pt) node[above right] {A}; \fill (3.5, 1.5) circle (2pt) node[above right] {B}; \end{tikzpicture} \end{center} In the diagram above: \begin{itemize} \item The Y-axis represents the Price and the X-axis represents the Quantity Demanded. \item DD is the demand curve, which slopes downwards from left to right. \item At the initial price , the quantity demanded is (Point A). \item When the price falls from to , the quantity demanded expands from to (a movement along the curve from Point A to Point B). This is called extension or expansion of demand. \item Conversely, if the price were to rise from to , the quantity demanded would contract from to . This is called contraction of demand. \end{itemize}

Step 4: Final Answer:
Changes in the price of a commodity cause a change in the quantity demanded, leading to a movement along the same demand curve. A decrease in price causes an expansion in demand, while an increase in price causes a contraction in demand, illustrating an inverse relationship.

Step 1: Meaning of Demand:
In economics, Demand refers to the quantity of a commodity that a consumer is willing and able to purchase at various possible prices during a given period of time. Demand is not just a mere desire; it must be backed by both the purchasing power (ability to buy) and the willingness to spend that money.

Step 2: Major Factors Affecting Demand (Determinants of Demand):
The demand for a commodity is influenced by several factors. The major ones are: \begin{enumerate} \item Price of the Commodity (Px): This is the most important factor. According to the Law of Demand, there is an inverse relationship between the price of a commodity and its quantity demanded, ceteris paribus. When the price falls, demand rises, and when the price rises, demand falls. \item Price of Related Goods (Pr): \begin{itemize} \item Substitute Goods: These are goods that can be used in place of each other (e.g., tea and coffee). An increase in the price of a substitute good leads to an increase in the demand for the given commodity (e.g., if the price of coffee rises, demand for tea will rise). \item Complementary Goods: These are goods that are used together to satisfy a want (e.g., car and petrol). An increase in the price of a complementary good leads to a decrease in the demand for the given commodity (e.g., if the price of petrol rises, the demand for cars may fall). \end{itemize} \item Income of the Consumer (Y): \begin{itemize} \item Normal Goods: For these goods, demand increases as consumer income increases. Most goods are normal goods. \item Inferior Goods: For these goods, demand decreases as consumer income increases. Consumers switch to better quality goods as their income rises. \end{itemize} \item Tastes and Preferences (T): The demand for a good is directly affected by the consumer's tastes, preferences, habits, and fashion. A favorable change in taste leads to an increase in demand. \item Expectations of Future Prices (E): If consumers expect the price of a commodity to rise in the future, they may increase their current demand to stock up. Conversely, if they expect a price fall, they may postpone their purchase, leading to a decrease in current demand. \end{enumerate}

Step 3: Final Answer:
Demand is the willingness and ability to buy a commodity at a given price. It is primarily affected by the commodity's own price, the price of related goods, consumer's income, tastes and preferences, and future price expectations.

Step 1: Statement of the Law:
The Law of Diminishing Marginal Utility states that as a consumer consumes more and more units of a specific commodity, the marginal utility (or additional satisfaction) derived from each successive unit goes on diminishing, assuming that the consumption of other commodities remains constant.

Step 2: Explanation with an Example (Schedule):
Let's consider a person who is very thirsty and drinks glasses of water. The satisfaction derived from each successive glass of water can be shown in a utility schedule.The table shows that as the person drinks more water, the Total Utility increases but at a decreasing rate, while the Marginal Utility from each additional glass continuously falls. After the 6th glass, TU is maximum, and MU is zero. The 7th glass leads to disutility (negative MU).

Step 3: Explanation with Diagram:
The relationship between Total Utility (TU) and Marginal Utility (MU) can be shown graphically. \begin{center} \begin{tikzpicture}[scale=0.9] % Upper panel for TU \begin{scope}[yshift=4cm] \draw[->] (0,0) -- (8,0) node[right] {Glasses of Water}; \draw[->] (0,0) -- (0,5) node[above] {Total Utility (TU)}; \draw[thick, color=blue] (0,0) .. controls (2,3.5) and (4,4.5) .. (6,4.5); \draw[thick, color=blue] (6,4.5) .. controls (6.5,4.4) and (7,4) .. (7.5,3.5); \node[above] at (4, 4.6) {TU}; \draw[dashed] (6, 4.5) -- (6, -2); \node at (6, 4.5) [circle,fill,inner sep=1.5pt]{}; \node[above] at (6, 4.5) {Maximum TU}; \end{scope} % Lower panel for MU \begin{scope}[yshift=0cm] \draw[->] (0,0) -- (8,0) node[right] {Glasses of Water}; \draw[->] (0,-2.5) -- (0,3) node[above] {Marginal Utility (MU)}; \draw[thick, color=red] (1,2.5) -- (6,0) -- (7.5, -1.5); \node[above] at (4, 1) {MU}; \node at (6, 0) [circle,fill,inner sep=1.5pt]{}; \node[below] at (6, 0) {MU=0}; \end{scope} \end{tikzpicture} \end{center} In the diagram, the TU curve rises, reaches a maximum when MU is zero, and then starts to fall when MU becomes negative. The MU curve slopes continuously downwards, illustrating the law of diminishing marginal utility.

Step 4: Final Answer:
The Law of Diminishing Marginal Utility explains that the satisfaction from consuming successive units of a good decreases. This is illustrated by a downward-sloping marginal utility curve and a total utility curve that increases at a decreasing rate.

Step 1: Understanding the Concept:
The question asks for the definition of Marginal Utility, a core concept in the theory of consumer behavior.

Step 2: Detailed Explanation:
Marginal Utility (MU) is the additional satisfaction or utility that a consumer gains from consuming one more unit of a good or service. The word 'marginal' in economics refers to the change associated with an additional unit.
The formula for marginal utility is: Where: \begin{itemize} \item is the marginal utility of the unit. \item is the total utility from consuming units. \item is the total utility from consuming units. \end{itemize} A key principle related to marginal utility is the Law of Diminishing Marginal Utility, which states that as a consumer consumes more and more units of a commodity, the marginal utility derived from each successive unit goes on diminishing.

Step 3: Final Answer:
Marginal Utility is the extra satisfaction a consumer gets from consuming one additional unit of a commodity.

Step 1: Understanding the Concept:
A demand curve parallel to the y-axis is a vertical straight line. This graphical representation shows that the quantity demanded of a commodity remains constant, regardless of any change in its price.

Step 2: Key Formula or Approach:
The formula for price elasticity of demand ( ) is:

Step 3: Detailed Explanation:
For a demand curve parallel to the y-axis, the quantity demanded does not change at all as the price changes. This means the change in quantity demanded ( ) is zero. Substituting this into the formula: This situation is known as perfectly inelastic demand. It typically applies to absolute necessities like life-saving drugs, where consumers will buy the same quantity irrespective of the price.

Step 4: Final Answer:
When the demand curve is parallel to the y-axis, the elasticity of demand is zero. Thus, option (A) is the correct answer.

Step 1: Understanding the Concept:
The Law of Equi-Marginal Utility describes how a consumer achieves maximum satisfaction by allocating their limited income among different goods. It states that a consumer will distribute their expenditure so that the marginal utility derived from the last unit of money spent on each good is equal.

Step 2: Detailed Explanation:
The development of marginal utility theory was a key event in the history of economic thought known as the "Marginal Revolution." \begin{itemize} \item William Stanley Jevons was one of the three main economists, along with Carl Menger and Léon Walras, who independently and almost simultaneously developed the theory of marginal utility in the 1870s. He was a foundational proponent (propounder) of using the marginal utility concept to explain consumer behavior.
\item While the idea was first articulated by H.H. Gossen (as Gossen's Second Law), it was Jevons who brought it to the forefront of economic debate in the English-speaking world.
\item Alfred Marshall later synthesized, refined, and popularized this law in his "Principles of Economics," giving it its modern name and formulation ( ).
\end{itemize} Given the options, Jevons is the most appropriate choice as a primary originator and proponent of the underlying theory.

Step 3: Final Answer:
The law of Equi-Marginal Utility was propounded by Jevons.

Step 1: Understanding Perfect Competition:
Under perfect competition, there are a very large number of buyers and sellers of a homogeneous product. No single buyer or seller can influence the market price. Therefore, the industry is the price-maker, and the individual firm is the price-taker.

Step 2: Price Determination by the Industry:
The market price is determined by the collective forces of market demand and market supply. \begin{itemize} \item Market Demand: The total quantity of a commodity demanded by all consumers at different prices. The market demand curve is downward sloping. \item Market Supply: The total quantity of a commodity supplied by all firms at different prices. The market supply curve is upward sloping. \end{itemize} The equilibrium price is established at the point where market demand equals market supply.

Step 3: Output Determination by the Firm:
The individual firm has to accept the equilibrium price determined by the industry. At this price, the firm can sell any quantity it wants. Hence, the demand curve for the firm is a horizontal line parallel to the X-axis (perfectly elastic). For a perfectly competitive firm, Price (P) = Average Revenue (AR) = Marginal Revenue (MR).
The firm's objective is to maximize profit. A firm is in equilibrium (and maximizes its profit) when two conditions are met: \begin{enumerate} \item Marginal Revenue (MR) = Marginal Cost (MC). \item The MC curve must cut the MR curve from below. \end{enumerate}

Step 4: Explanation with Diagram:
In the left panel (Industry), the equilibrium price is determined at point E, where the demand curve DD and supply curve SS intersect. In the right panel (Firm), the firm takes this price as given. The firm produces output, where its MC curve cuts the MR curve at point 'e', thus maximizing its profit.

Solution (Calculation of MPC and APC):

Step 1: Understanding the Concepts and Formulas:
\begin{itemize} \item Average Propensity to Consume (APC): The ratio of total consumption (C) to total income (Y). It shows the proportion of income that is consumed. \item Marginal Propensity to Consume (MPC): The ratio of the change in consumption ( ) to the change in income ( ). It shows the proportion of additional income that is consumed. \end{itemize}

Step 2: Organizing the Data and Calculations:
We will create a table to calculate the required values from the given data.

Step 3: Final Answer:
The calculated values are as follows: \begin{itemize} \item Average Propensity to Consume (APC): \begin{itemize} \item At an income of Rupees 50, APC is 1.20. \item At an income of Rupees 100, APC is 1.00. \item At an income of Rupees 150, APC is 0.80. \end{itemize} \item Marginal Propensity to Consume (MPC): \begin{itemize} \item When income increases from Rupees 50 to Rupees100, MPC is 0.80. \item When income increases from Rupees 100 to Rupees150, MPC is 0.40. \end{itemize} \end{itemize}

Step 1: Statement of the Law:
The Law of Variable Proportions (or the Law of Diminishing Marginal Returns) states that in the short run, when some factors of production are fixed and one factor is variable, as we increase the quantity of the variable factor, the Total Product (TP) initially increases at an increasing rate, then at a diminishing rate, and finally starts to decline. Consequently, the Marginal Product (MP) of the variable factor first increases, reaches a maximum, then falls, becomes zero, and finally becomes negative.

Step 2: Explanation of the Three Stages:
The law operates in three distinct stages: \begin{enumerate} \item Stage I: Increasing Returns to a Factor. In this stage, the Total Product (TP) increases at an increasing rate, and the Marginal Product (MP) of the variable factor increases. This is due to better utilization of the fixed factor and increased efficiency of the variable factor. \item Stage II: Diminishing Returns to a Factor. In this stage, the Total Product (TP) continues to increase but at a diminishing rate, and the Marginal Product (MP) falls but remains positive. This stage ends when TP is at its maximum and MP is zero. This is the rational stage of production for a firm. \item Stage III: Negative Returns to a Factor. In this stage, the Total Product (TP) starts to decline, and the Marginal Product (MP) becomes negative. This is because the quantity of the variable factor is too high in relation to the fixed factor, leading to overcrowding and inefficiency. \end{enumerate}

Step 3: Explanation with Diagram:
The relationship between TP and MP and the three stages can be shown with the help of the following diagram: \begin{center} \begin{tikzpicture}[scale=1] % Upper panel for TP \begin{scope}[yshift=4cm] \draw[->] (0,0) -- (8,0) node[right] {Units of Variable Factor}; \draw[->] (0,0) -- (0,4) node[above] {Total Product (TP)}; \draw[thick, color=blue] (0,0) .. controls (1,1) and (2,3.5) .. (2.5,3.8); % Increasing returns \draw[thick, color=blue] (2.5,3.8) .. controls (3.5,4.3) and (4.5,4.5) .. (5,4.5); % Diminishing returns \draw[thick, color=blue] (5,4.5) .. controls (5.5,4.4) and (6.5,4) .. (7,3.5); % Negative returns \node[above] at (3.5, 4.5) {TP}; \draw[dashed] (2.5, 3.8) -- (2.5, -2); \draw[dashed] (5, 4.5) -- (5, -2); \node at (1.25, -0.5) {Stage I}; \node at (3.75, -0.5) {Stage II}; \node at (6, -0.5) {Stage III}; \node at (2.5, 3.8) [circle,fill,inner sep=1pt]{}; \node at (5, 4.5) [circle,fill,inner sep=1pt]{}; \node[above] at (2.5,3.8) {Point of Inflection}; \node[above] at (5,4.5) {Max TP}; \end{scope} % Lower panel for MP \begin{scope}[yshift=0cm] \draw[->] (0,0) -- (8,0) node[right] {Units of Variable Factor}; \draw[->] (0,-1) -- (0,3) node[above] {Marginal Product (MP)}; \draw[thick, color=red] (0,0) .. controls (1.5,2.5) and (2,2.5) .. (2.5,2); \draw[thick, color=red] (2.5,2) .. controls (3.5,1) and (4,0.5) .. (5,0); \draw[thick, color=red] (5,0) .. controls (5.5,-0.2) and (6.5,-0.5) .. (7,-0.8); \node[above] at (3.5, 1.5) {MP}; \draw[dashed] (2.5, 2) -- (2.5, 2); \node at (2.5, 2) [circle,fill,inner sep=1pt]{}; \node at (5, 0) [circle,fill,inner sep=1pt]{}; \end{scope} \end{tikzpicture} \end{center}

Solution (Law of Supply):

Step 1: Statement of the Law:
The Law of Supply states that, other things being equal (ceteris paribus), there is a direct relationship between the price of a commodity and its quantity supplied. This means that as the price of a commodity increases, its quantity supplied by producers also increases, and as the price decreases, the quantity supplied also decreases. This is primarily due to the profit motive; a higher price makes it more profitable for firms to produce and sell more.

Step 2: Supply Schedule:
A supply schedule is a table that shows the quantity of a good that a producer is willing and able to supply at different prices over a given period of time. \begin{center} Supply Schedule for Good XThe schedule clearly shows that as the price increases from Rupees10 to Rupees40, the quantity supplied increases from 100 to 400 units.

Step 3: Supply Curve:
A supply curve is a graphical representation of the supply schedule. It plots the relationship between price and quantity supplied. \begin{center} \begin{tikzpicture} \draw[->] (0,0) -- (5,0) node[right] {Quantity Supplied}; \draw[->] (0,0) -- (0,5) node[above] {Price}; \draw[thick, color=green] (1,1) -- (4,4) node[right] {SS (Supply Curve)}; \draw[dashed] (1,1) -- (1,0) node[below] {100}; \draw[dashed] (1,1) -- (0,1) node[left] {10}; \draw[dashed] (2,2) -- (2,0) node[below] {200}; \draw[dashed] (2,2) -- (0,2) node[left] {20}; \draw[dashed] (3,3) -- (3,0) node[below] {300}; \draw[dashed] (3,3) -- (0,3) node[left] {30}; \fill (1,1) circle (2pt); \fill (2,2) circle (2pt); \fill (3,3) circle (2pt); \fill (4,4) circle (2pt); \end{tikzpicture} \end{center} In the diagram, the supply curve SS slopes upwards from left to right, indicating the direct relationship between price and quantity supplied.

Step 4: Final Answer:
The Law of Supply describes a direct relationship between price and quantity supplied. This is demonstrated by a supply schedule, which shows higher quantities supplied at higher prices, and a corresponding upward-sloping supply curve.

Step 1: Meaning of Production Cost:
Production Cost refers to the total expenditure incurred by a firm in the process of producing a certain level of output. It includes all the payments made to the factors of production (like wages to labor, rent for land, interest on capital) and on non-factor inputs (like raw materials, fuel, power).
Costs are generally divided into two types: \begin{itemize} \item Explicit Costs: Direct, out-of-pocket payments made by a firm for inputs, such as wages, rent, and raw material costs. \item Implicit Costs: The imputed value of the inputs owned and used by the firm in its own production process, such as the salary the owner could have earned elsewhere. \end{itemize} Total Production Cost = Explicit Costs + Implicit Costs.

Step 2: Explanation of Average Cost:
Average Cost (AC), also known as Average Total Cost (ATC), is the per-unit cost of production. It is calculated by dividing the Total Cost (TC) by the total quantity of output (Q) produced. Average cost is the sum of Average Fixed Cost (AFC) and Average Variable Cost (AVC). \begin{itemize} \item AFC ( ) continuously falls as output increases. \item AVC ( ) first falls, reaches a minimum, and then rises due to the law of variable proportions. \end{itemize} The Average Cost curve is typically U-shaped. It falls initially because of increasing returns and economies of scale. After reaching a minimum point, it starts to rise because of diminishing returns and diseconomies of scale. The initial fall in AC is due to the fall in both AFC and AVC. The eventual rise in AC is because the sharp rise in AVC outweighs the continuous fall in AFC.

Step 3: Explanation with Diagram:
\begin{center} \begin{tikzpicture}[scale=0.9] \draw[->] (0,0) -- (7,0) node[right] {Output (Q)}; \draw[->] (0,0) -- (0,5) node[above] {Cost}; \draw[thick, color=red, domain=0.5:6] plot (\x, {2.5/\x}) node[right] {AFC}; \draw[thick, color=green] (1,3) .. controls (2.5,1) and (3.5,1.2) .. (6,4) node[right] {AVC}; \draw[thick, color=blue] (1,4.5) .. controls (3,1.8) and (4.5,2) .. (6,4.5) node[right] {AC}; \draw[thick, color=purple, domain=1:6] plot (\x, {0.2*(\x-3.5)^2 + 1.5}) node[right] {MC}; \end{tikzpicture} \end{center} In the diagram: \begin{itemize} \item The Y-axis represents Cost and the X-axis represents Output. \item The AC curve is shown in blue. It is U-shaped, first decreasing, reaching a minimum, and then increasing. \item The shape of the AC curve is a result of its components: the continuously falling AFC curve (red) and the U-shaped AVC curve (green). \item The Marginal Cost (MC) curve (purple) is also shown, which cuts the AC curve at its lowest point. \end{itemize}

Step 4: Final Answer:
Production cost is the total expenditure on inputs for production. Average cost is the per-unit cost of production (TC/Q). The AC curve is U-shaped because it initially falls due to economies of scale and then rises due to diseconomies of scale.

Step 1: Understanding the Concept of Consumer's Equilibrium:
Consumer's Equilibrium refers to a situation in which a consumer derives maximum satisfaction from the consumption of goods and services, given their limited income and the market prices of the goods. At this point, the consumer has no tendency to change their pattern of expenditure. It is a point of optimal choice.

Step 2: Consumer's Equilibrium with Indifference Curve Analysis:
To show consumer's equilibrium using indifference curve analysis, we need two tools: \begin{enumerate} \item Indifference Map: This represents the consumer's preferences for different combinations of two goods. Higher indifference curves represent higher levels of satisfaction. \item Budget Line: This represents all the combinations of two goods that a consumer can afford to buy with their given income and the prices of the two goods. \end{enumerate}

Step 3: Conditions for Equilibrium:
A consumer is in equilibrium when they reach the highest possible indifference curve, given their budget line. This occurs at the point where the budget line is tangent to an indifference curve. The two conditions for equilibrium are: \begin{enumerate} \item The budget line must be tangent to the indifference curve. At this point, the slope of the indifference curve must be equal to the slope of the budget line. Where is the Marginal Rate of Substitution between Good X and Good Y, and is the ratio of their prices. \item The indifference curve must be convex to the origin at the point of equilibrium. This ensures that the MRS is diminishing, which is a necessary condition for a stable equilibrium. \end{enumerate}

Step 4: Explanation with Diagram:
\begin{center} \begin{tikzpicture}[scale=0.9] \draw[->] (0,0) -- (7,0) node[right] {Good X}; \draw[->] (0,0) -- (0,5) node[above] {Good Y}; \draw[thick, color=red] (0,4) -- (6,0) node[midway, above, sloped] {Budget Line (AB)}; \draw[color=blue, domain=0.8:6] plot (\x, {6/\x}) node[right] { }; \draw[color=blue, domain=1.2:6] plot (\x, {10/\x}) node[right] { }; \draw[color=blue, domain=2:6] plot (\x, {16/\x}) node[right] { }; \fill (3, 2) circle (2pt) node[above right] {E (Equilibrium)}; \draw[dashed] (3, 2) -- (3, 0) node[below] { }; \draw[dashed] (3, 2) -- (0, 2) node[left] { }; \node at (1.5, 4) {R}; \node at (4.5, 1) {S}; \fill (1.5, 4) circle (1.5pt); \fill (4.5, 1) circle (1.5pt); \end{tikzpicture} \end{center} In the diagram: \begin{itemize} \item AB is the budget line. \item , , and are indifference curves, with representing the highest satisfaction. \item The consumer can afford points R and S on , but this is not the maximum satisfaction they can achieve. \item The consumer cannot afford any point on as it is beyond the budget line. \item The optimal point is E, where the budget line AB is tangent to the highest attainable indifference curve, . At this point, the consumer buys units of Good X and units of Good Y, and the two conditions for equilibrium ( and convexity of IC) are met. \end{itemize}

Step 5: Final Answer:
A consumer is in equilibrium when they maximize their satisfaction subject to their budget constraint. Using indifference curve analysis, this equilibrium is achieved at the point where the budget line is tangent to the highest possible indifference curve.

Step 1: Understanding the Concept:
Price Elasticity of Demand measures the responsiveness of the quantity demanded of a good to a change in its price. The question asks for three factors that influence this responsiveness.

Step 2: Detailed Explanation:
Three key factors affecting the Price Elasticity of Demand are: \begin{enumerate}[label=\arabic*.] \item Availability of Close Substitutes: \begin{itemize} \item If a good has many close substitutes (e.g., Pepsi and Coke), its demand is highly elastic. A small increase in the price of one will cause consumers to switch to the other, leading to a large drop in quantity demanded. \item If a good has few or no close substitutes (e.g., salt, life-saving drugs), its demand is inelastic. Consumers have no alternative, so they will continue to buy it even if the price increases. \end{itemize} \item Nature of the Commodity: \begin{itemize} \item Necessities (e.g., food, medicine) have inelastic demand because consumers need them regardless of the price. \item Luxuries (e.g., sports cars, designer clothes) have elastic demand because their consumption can be easily postponed or avoided if the price rises. \end{itemize} \item Proportion of Income Spent on the Good: \begin{itemize} \item Goods on which a consumer spends a very small proportion of their income (e.g., a matchbox, a newspaper) tend to have inelastic demand. A price change doesn't significantly impact the consumer's budget. \item Goods on which a consumer spends a large part of their income (e.g., a car, a house) have elastic demand. A price increase will have a major impact on the budget, making the consumer very responsive to the price change. \end{itemize} \end{enumerate}

Step 3: Final Answer:
Three factors affecting the elasticity of demand are the availability of close substitutes, the nature of the commodity (necessity vs. luxury), and the proportion of income spent on the good.

Step 1: Understanding the Concept:
The question asks for the definition of a production function, a fundamental concept in the theory of production in microeconomics.

Step 2: Detailed Explanation:
A production function is a technological relationship that expresses the maximum quantity of a good that can be produced from a given set of inputs (factors of production), over a specific period of time, assuming a given state of technology.
In simple terms, it shows the relationship between physical inputs and physical output.
It can be expressed mathematically as: Where: \begin{itemize} \item is the maximum quantity of output of good X. \item denotes the functional relationship. \item is the quantity of labor used. \item is the quantity of capital used. \end{itemize} The production function is a purely technical concept and does not involve prices or costs. It simply describes what is technically feasible when the firm operates efficiently.

Step 3: Final Answer:
A production function is a technical relationship that shows the maximum amount of output that can be produced with a given combination of inputs, such as labor and capital, under a given state of technology.

Step 1: Understanding the Concept:
Marginal Cost (MC) is the additional cost incurred in the production of one more unit of a good or service.

Step 2: Key Formula or Approach:
The formula for marginal cost is the change in total cost ( ) divided by the change in the number of units produced ( ). When producing just one more unit ( ), the formula simplifies.

Step 3: Detailed Explanation:
To find the marginal cost of the unit, we subtract the total cost of producing the previous units from the total cost of producing units.
This is represented by the formula:
Let's analyze the other options: \begin{itemize} \item (A) is incorrect because Total Fixed Cost (TFC) does not change with output, so its difference would be zero. \item (B) and (C) are incorrect as they represent the change in average costs, not the marginal cost itself. \end{itemize}

Step 4: Final Answer:
The correct formula for calculating the marginal cost of the unit is . Thus, option (D) is correct.

Step 1: Understanding the Concept:
Average Fixed Cost (AFC) is the total fixed cost (TFC) per unit of output. Fixed costs are costs that do not change with the level of production (e.g., rent, machinery cost).

Step 2: Key Formula or Approach:
The formula for AFC is: where is Total Fixed Cost and is the quantity of output.

Step 3: Detailed Explanation:
In this formula, TFC is a constant value. As the quantity of output ( ) increases, this constant TFC is divided by a larger and larger number.
Consequently, the value of AFC continuously falls as more units are produced.
The AFC curve is a downward-sloping curve that gets closer and closer to the X-axis but never touches it. This shape is known as a rectangular hyperbola.
Therefore, the statement that the AFC curve "falls, as more units are produced" is correct.

Step 4: Final Answer:
Since AFC is calculated by dividing a constant TFC by an increasing quantity Q, its value continuously decreases. Thus, option (C) is the correct answer.

Step 1: Define Equi-Marginal Utility.
The Law of Equi-Marginal Utility states that a consumer will allocate their limited income between goods in such a way that the marginal utility per unit of money spent is equal for all goods. This maximizes total satisfaction or utility.
Step 2: Mathematical Representation.
If a consumer spends their income on goods and , the equilibrium condition for the consumer is: where and represent the marginal utilities of goods and , and and are their respective prices. The consumer reaches equilibrium when the ratio of marginal utility to price is the same for all goods.
Step 3: Diagrammatic Representation.
In an indifference curve diagram, the consumer's equilibrium is achieved where the budget line is tangent to the highest possible indifference curve. This represents the point at which the consumer cannot increase utility by reallocating their income.
Step 4: Conclusion.
Thus, the law of equi-marginal utility explains how consumers make choices to maximize their satisfaction by equalizing the marginal utility per unit of money spent on each good. Final Answer:

Step 1: Define the law of diminishing marginal rate of substitution (MRS).
The law of diminishing marginal rate of substitution states that as a consumer moves along an indifference curve and substitutes one good for another, the marginal rate of substitution (MRS) between the two goods diminishes. In simple terms, as the consumer consumes more of one good and less of another, they are willing to give up less and less of the second good to get more of the first good.
Step 2: Explanation of MRS.
The marginal rate of substitution is the slope of the indifference curve, which shows the amount of one good that a consumer is willing to give up for an additional unit of another good, while maintaining the same level of satisfaction.
Step 3: Diagram and diminishing MRS.
In the diagram of an indifference curve, as we move down along the curve from left to right, the consumer substitutes more of good X for good Y. The rate at which good Y is given up decreases as more of good X is consumed, hence the slope of the curve flattens.
Step 4: Conclusion.
Thus, the law of diminishing marginal rate of substitution implies that as a consumer substitutes goods, the amount of one good that they are willing to give up for an additional unit of the other good decreases. Final Answer:

Step 1: Understanding the Concept:
Consumer's Equilibrium is a point of maximum satisfaction for a consumer. It is a situation where a consumer spends their limited income on different goods in such a way that their total utility is maximized. At this point, the consumer has no tendency to change their consumption pattern. Indifference curve analysis (or Ordinal Utility Analysis) explains this equilibrium.

Step 2: Tools and Conditions for Equilibrium:
The equilibrium is determined using two tools: \begin{enumerate} \item Indifference Map: This represents the consumer's preferences, with higher indifference curves (ICs) showing higher levels of satisfaction. \item Budget Line: This represents the consumer's income and the prices of goods, showing all affordable combinations. \end{enumerate} The consumer reaches equilibrium when two conditions are met: \begin{enumerate} \item The budget line is tangent to the highest possible indifference curve. At this point, the slope of the IC equals the slope of the budget line. (Where MRS is the Marginal Rate of Substitution, and are prices of goods X and Y). \item The indifference curve must be convex to the origin at the point of tangency. This implies a diminishing MRS. \end{enumerate}

Step 3: Explanation with Diagram:
\begin{center} \begin{tikzpicture}[scale=0.9] \draw[->] (0,0) -- (7,0) node[right] {Good X}; \draw[->] (0,0) -- (0,5) node[above] {Good Y}; \draw[thick, color=red] (0,4) -- (6,0) node[midway, above, sloped] {Budget Line (AB)}; \draw[color=blue, domain=0.8:6] plot (\x, {6/\x}) node[right] { }; \draw[color=blue, domain=1.2:6] plot (\x, {10/\x}) node[right] { }; \draw[color=blue, domain=2:6] plot (\x, {16/\x}) node[right] { }; \fill (3, 2) circle (2pt) node[above right] {E (Equilibrium)}; \draw[dashed] (3, 2) -- (3, 0) node[below] { }; \draw[dashed] (3, 2) -- (0, 2) node[left] { }; \end{tikzpicture} \end{center} In the diagram, the consumer can afford any point on the budget line AB. Points on are attainable but offer less satisfaction. Points on offer more satisfaction but are unaffordable. The optimal choice is point E, where the budget line is tangent to the highest possible indifference curve, . At this point, the consumer maximizes their satisfaction by purchasing of Good X and of Good Y.
Solution (Calculation of Elasticity of Demand):

Step 1: Understanding the Concept and Formula:
The question asks for the Price Elasticity of Demand ( ), which measures how responsive the quantity demanded is to a price change. We use the percentage method. Where P = Initial Price, Q = Initial Quantity, = Change in Price, and = Change in Quantity.

Step 2: Identifying the Given Values:
\begin{itemize} \item Initial Price (P) = Rupees 10 \item New Price ( ) = Rupees 11 \item Initial Quantity (Q) = 100 units \item New Quantity ( ) = 90 units \end{itemize}

Step 3: Calculating the Changes:
\begin{itemize} \item Change in Price ( ) = \item Change in Quantity ( ) = \end{itemize}

Step 4: Substituting the Values and Calculating:
Step 5: Final Answer and Interpretation:
The price elasticity of demand is 1.
Since , the demand is unitary elastic. This means the percentage change in quantity demanded (-10%) is exactly equal to the percentage change in price (+10%).

Step 1: Understanding the Concept:
Price elasticity of demand ( ) measures the degree of responsiveness of the quantity demanded of a good to a change in its price. There are five main degrees of price elasticity.

Step 2: Explanation of Degrees with Diagrams:
\begin{enumerate} \item Perfectly Elastic Demand ( ): A situation where a small or no change in price leads to an infinite change in quantity demanded. The demand curve is a horizontal line parallel to the X-axis. \begin{center} \begin{tikzpicture}[scale=0.6] \draw[->] (0,0) -- (5,0) node[right] {Q}; \draw[->] (0,0) -- (0,4) node[above] {P}; \draw[thick] (0,2.5) -- (4,2.5) node[right] {D}; \draw[dashed] (0,2.5) -- (0,2.5) node[left] {P*}; \end{tikzpicture} \end{center} \item Perfectly Inelastic Demand ( ): A situation where the quantity demanded does not change at all, irrespective of the change in price. The demand curve is a vertical line parallel to the Y-axis. \begin{center} \begin{tikzpicture}[scale=0.6] \draw[->] (0,0) -- (5,0) node[right] {Q}; \draw[->] (0,0) -- (0,4) node[above] {P}; \draw[thick] (2.5,0) -- (2.5,3.5) node[above] {D}; \draw[dashed] (2.5,0) -- (2.5,0) node[below] {Q*}; \end{tikzpicture} \end{center} \item Unitary Elastic Demand ( ): A situation where the percentage change in quantity demanded is exactly equal to the percentage change in price. The demand curve is a rectangular hyperbola. \begin{center} \begin{tikzpicture}[scale=0.6] \draw[->] (0,0) -- (5,0) node[right] {Q}; \draw[->] (0,0) -- (0,4) node[above] {P}; \draw[thick, domain=0.8:4.5] plot (\x, {4/\x}) node[right] {D}; \end{tikzpicture} \end{center} \item Relatively Elastic Demand ( ): A situation where the percentage change in quantity demanded is greater than the percentage change in price. The demand curve is relatively flat. \begin{center} \begin{tikzpicture}[scale=0.6] \draw[->] (0,0) -- (5,0) node[right] {Q}; \draw[->] (0,0) -- (0,4) node[above] {P}; \draw[thick] (1,3.5) -- (4,1) node[right] {D}; \end{tikzpicture} \end{center} \item Relatively Inelastic Demand ( ): A situation where the percentage change in quantity demanded is less than the percentage change in price. The demand curve is relatively steep. \begin{center} \begin{tikzpicture}[scale=0.6] \draw[->] (0,0) -- (5,0) node[right] {Q}; \draw[->] (0,0) -- (0,4) node[above] {P}; \draw[thick] (1,3.5) -- (3,1) node[right] {D}; \end{tikzpicture} \end{center} \end{enumerate}

Step 3: Final Answer:
The five degrees of elasticity of demand are perfectly elastic ( ), perfectly inelastic ( ), unitary elastic ( ), relatively elastic ( ), and relatively inelastic ( ), each represented by a demand curve with a distinct shape.

Step 1: Understanding the Concept:
The question asks for the definition of utility, a fundamental concept in the theory of consumer behavior.

Step 2: Detailed Explanation:
In economics, Utility refers to the want-satisfying power of a commodity or a service. It is the amount of satisfaction, pleasure, or benefit that a consumer derives from the consumption of a good.
Key characteristics of utility are: \begin{itemize}[noitemsep] \item It is subjective: Utility varies from person to person, place to place, and time to time. A cup of coffee may provide high utility to one person but none to another. \item It is not the same as usefulness: A commodity may have utility but may not be useful. For example, cigarettes have utility for a smoker but are harmful to health. \item It is ethically neutral: The concept of utility does not involve any moral or ethical judgments. \end{itemize} Economists use this concept to explain how consumers make choices to maximize their satisfaction.

Step 3: Final Answer:
Utility is the capacity of a good or service to satisfy a human want. It is the measure of satisfaction a consumer receives from consuming a product.

Step 1: Understanding the Concept:
A demand curve parallel to the x-axis is a horizontal line. This indicates that consumers are willing to buy an unlimited quantity of a good at a specific price, but if the price increases even slightly, the quantity demanded drops to zero.

Step 2: Detailed Explanation:
This situation represents perfectly elastic demand. The formula for price elasticity of demand ( ) is the percentage change in quantity demanded divided by the percentage change in price. For a horizontal demand curve, a tiny (near-zero) percentage change in price leads to an infinitely large percentage change in quantity demanded. Mathematically, any number divided by zero is infinite. Therefore, the elasticity of demand is infinite.

Step 3: Final Answer:
If the demand curve is parallel to the x-axis, the elasticity of demand is infinite. Therefore, option (A) is correct.

Step 1: Understanding the Concept:
Average Utility (AU) is a measure of the per-unit satisfaction a consumer gets from a good. It is derived from the concept of Total Utility (TU), which is the total satisfaction obtained from consuming all units of a good.

Step 2: Detailed Explanation:
The formula for Average Utility is: where: \begin{itemize} \item = Average Utility \item = Total Utility \item = Quantity of the commodity consumed \end{itemize} For example, if consuming 4 apples gives a total utility of 40 utils, the average utility is: Average utility is different from marginal utility, which is the additional utility gained from consuming one more unit of the good. Generally, as consumption increases, both average and marginal utility tend to decrease.

Step 1: Understanding the Concept:
Indifference curves are a tool used in microeconomics to represent consumer preferences. They are the foundation of ordinal utility analysis.

Step 2: Detailed Explanation and Properties:
\begin{itemize} \item Graphical Representation: It is a curve where each point represents a "bundle" of two goods. \item Equal Satisfaction: Every point on a single indifference curve yields the same level of total utility. A consumer would be equally happy with any combination on that curve. \item Key Properties: \begin{enumerate} \item Downward Sloping: To get more of one good, the consumer must give up some of the other good to maintain the same level of satisfaction. \item Convex to the Origin: This reflects the principle of diminishing marginal rate of substitution (MRS). As a consumer has more of Good X, they are willing to give up less of Good Y to get an additional unit of X. \item Higher Curves Represent Higher Utility: An indifference curve that is further to the right and above another represents a higher level of satisfaction. \item They Never Intersect: Intersection would violate the assumption of transitivity and consistency in consumer preferences. \end{enumerate} \end{itemize}

Step 1: Understand the concept of indifference curve.
An indifference curve represents a set of combinations of two goods that give a consumer the same level of satisfaction or utility. The consumer is indifferent between these combinations.
Step 2: Higher indifference curves.
When an indifference curve shifts to a higher position (i.e., farther from the origin), it represents a higher level of satisfaction because it reflects combinations of goods that provide more of one or both goods, hence increasing total utility.
Step 3: Conclusion.
Thus, a higher indifference curve represents a higher level of satisfaction, as it indicates that the consumer can achieve more of the desired goods while maintaining the same level of utility. Final Answer:

Step 1: Concept of average revenue and marginal revenue.
In a perfectly competitive market, average revenue (AR) refers to the revenue per unit of output, and marginal revenue (MR) refers to the additional revenue from selling one more unit of output. In a perfectly competitive market, both are equal to the price of the good.
Step 2: Perfect competition characteristics.
In a perfectly competitive market, firms are price takers, meaning they cannot influence the market price. Therefore, the price of the good is constant, and thus average revenue and marginal revenue are equal.
Step 3: Conclusion.
Thus, the correct answer is (A) Average Revenue (AR) = Marginal Revenue (MR). Final Answer:

Step 1: Understand the concept of marginal utility.
Marginal utility is the additional satisfaction or benefit derived from consuming one more unit of a good or service. When marginal utility is positive, total utility increases with each additional unit consumed. However, once marginal utility becomes negative, the consumption of additional units reduces total satisfaction.
Step 2: Impact of negative marginal utility on total utility.
When marginal utility becomes negative, the total utility stops increasing and begins to decrease. This is because the additional consumption of a good or service leads to a decrease in overall satisfaction.
Step 3: Conclusion.
Thus, the correct answer is (B) the total utility decreases, as negative marginal utility implies a reduction in total satisfaction. Final Answer: