Rosie's Flower Shop Sells Bouquets of Roses for $15 Each

Rosie's Flower Shop sells bouquets of roses for $15 each.If Rosie hires 10 workers,she can sell 500 bouquets per week.If she hires 11 workers,she can sell 560 bouquets per week.Rosie pays each of her workers $400 per week.Which of the following is correct?

A) For the 11th worker, the marginal profit is $500.
B) For the 11th worker, the marginal revenue product is $500.
C) The firm is maximizing its profit.
D) If the firm is employing 11 workers, then its profit would increase if it cut back to 10 workers.