In the case of a monopolist, what is the nature of the supply curve?

Introduction / Context:
In perfect competition, we can derive a firm's supply curve from its marginal cost curve above the shutdown point. However, the situation is different under monopoly. This question asks about the nature of the supply curve for a monopolist and tests your understanding that for a single seller in a market, there is no well defined supply curve independent of demand.

Given Data / Assumptions:
- The market structure considered is monopoly. - We are asked about the monopolist's supply curve. - Options suggest various shapes: vertical, horizontal, downward sloping, or non existent. - We assume standard microeconomic theory of monopoly pricing and output.

Concept / Approach:
In monopoly, the firm is the industry and faces the entire market demand curve. Output and price are determined simultaneously by equating marginal revenue and marginal cost, taking the demand curve into account. Because different demand curves can lead to different quantities supplied at the same marginal cost, there is no unique mapping from price to quantity supplied that is independent of demand. For this reason, economists say that a monopolist does not have a supply curve in the same sense as a competitive firm.

Step-by-Step Solution:
Step 1: Recall that a competitive firm takes price as given and chooses output where price equals marginal cost, giving a clear relationship between price and quantity supplied. Step 2: In contrast, a monopolist chooses both price and quantity by setting marginal revenue equal to marginal cost and then reading the corresponding price from the demand curve. Step 3: Because marginal revenue depends on the shape of the demand curve, a change in demand can change the quantity supplied even if marginal cost is unchanged. Step 4: Therefore, there is no single curve that shows quantity supplied at each possible price independently of demand. Step 5: Among the options, the statement that the supply curve does not exist as a separate curve correctly reflects this reasoning.

Verification / Alternative check:
Standard microeconomics textbooks explicitly state that a monopolist has no supply curve analogous to that of a competitive firm. Instead, we analyse monopoly using the demand curve, marginal revenue, and marginal cost together. If a monopolist were to face different demand conditions, the same marginal cost function could lead to different combinations of price and output, confirming there is no unique supply schedule.

Why Other Options Are Wrong:
Option a, vertical, would imply quantity is fixed regardless of price, which is not how monopoly works. Option b, horizontal, would correspond to a perfectly elastic supply, which conflicts with monopoly power. Option c, downward sloping, incorrectly suggests that as price decreases, the monopolist supplies more, which confuses supply with demand. None of these shapes captures the fact that monopoly output decisions depend on the interaction of marginal cost and demand, not on a separate supply curve.

Common Pitfalls:
Students sometimes think that because a monopolist produces less at higher prices, its supply curve must be downward sloping, accidentally mixing up demand and supply. Another pitfall is to assume that every firm must always have a supply curve, regardless of market structure. Remembering that monopoly involves simultaneous determination of price and quantity, and that no independent supply function exists, helps you answer correctly.

Final Answer:
For a monopolist, a separate supply curve does not exist in the usual sense used for competitive firms.