A Competitive Firm Sells Its Output for $50 Per Unit

Multiple Choice

A competitive firm sells its output for $50 per unit. Assume that labor is the only input that varies for the firm. The marginal product of the 10th worker is 10 units of output per day; the marginal product of the 11th worker is 8 units of output per day. The firm pays its workers a wage of $160 per day. For the 10th worker, the value of the marginal product of labor is

A) $250.
B) $400.
C) $500.
D) $1,280.