Like competitive firms, monopolies charge a price equal to marginal cost

Market demand curves may slope downward even if some individual demand curves do not because

A. the law of demand requires that this is true. B. lower prices may bring more purchasers into the market. C. merchants try to sell more at lower prices. D. people believe expensive goods are better goods.

Below, the graph on the left shows the short-run cost curves for a firm in a perfectly competitive market, and the graph on the right shows the current market conditions in this industry. In order to maximize profit, how much output should the firm produce?

A. 60 units B. 80 units C. 20 units D. 40 units E. 50 units