A firm will maximize its profits by hiring factors up to the point at which:
a. MR = MC, if the firm is a monopolist, monopolistic competitor, or oligopolist.
b. P = MC, if the firm is a perfect competitor.
c. MRP = MFC, if the firm is a product price taker.
d. VMP = MFC, if the firm is a product price searcher.
e. a and b