Choice "A" is correct. No matter which model is representative of the industry in which the firm operates, the firm will maximize profits by producing at MR. In order to sell at the rate of output in markets controlled by monopolists, the price is set where marginal revenue equals marginal cost. The monopolist's price will be higher than MR resulting in large profits.
Choice "d" is incorrect. Price exceeds both MR and MC.
Choices "c" and "b" are incorrect, which are far-out distractors.
