Suppose the wholesale market for corn is a perfectly competitive market, and all firms in the corn industry are profit-maximizing firms. Consider that the market is in short-run equilibrium. Which of the following statements are correctChoose one or more: A. All firms selling corn must have the same marginal cost, regardless of each firm's cost structure. B. Firms that choose not to sell in this market must be earning exactly zero profit. C. Total costs for each firm in the market may be different. D. All firms in the market must be making either positive profits, or exactly zero profit. E. All firms in the market must be earning identical profits.