If a firm's marginal revenue exceeds its marginal cost, maximum-profit rules require that the firm: a. increase its output in both perfect and imperfect competition. b. increase its output in perfect but not necessarily in imperfect competition. c. increase its output in imperfect but not necessarily in perfect competition. d. decrease its output in both perfect and imperfect competition. e. increase price, not output, in both perfect and imperfect competition.