21. Using the above figure, which of the following statements is true?
(A)At point e, the marginal cost of the last unit produced is equal to the price, therefore to maximize its profit the firm should produce no more nor less.
(B)At point f, the marginal revenue of the last unit produced is equal to the marginal cost, therefore to maximize its profit the firm should produce no more nor less.
(C) At point f, the marginal revenue of the last unit produced is greater than the marginal cost, therefore to maximize its profit the firm should produce more.
(D) At point d, the marginal revenue of the last unit produced is less than the marginal cost, therefore the firm should produce more.