Which of the following statements is true for both a monopolistically competitive firm and a perfectly competitive firm in long-run profit-maximizing equilibrium?
A) Economic profits equal zero, and price equals marginal cost.
B) Economic profits equal zero, and price equals marginal revenue.
C) Marginal revenue equals marginal cost and profits are positive.
D) Economic profits equal zero, and marginal revenue equals marginal cost.
E) Economic profits equal zero, and price exceeds marginal cost.