15. Which of the following statements is correct regarding profit-maximizing firms in the long run?
(A) In perfect competition, firms produce an output at which price is less than marginal cost.
(B) In perfect competition, firms produce an output at which price is greater than marginal cost.
(C) In monopolistic competition, firms produce less than the output at which average total cost isminimized.
(D) In monopolistic competition, firms produce more than the output at which average total cost isminimized.