Suppose That One Knows That Firm a Is Maximizing Profit

Suppose that one knows that firm A is maximizing profit and is paying a wage rate of $10 to its workers.It must therefore be true that

A) the firm is a perfect competitor in the labour market.
B) the value of the marginal product of the last worker is greater than $10.
C) the firm is a monopsonist.
D) the value of marginal product of the last worker is less than $10.
E) the extra cost of hiring the last worker was greater than or equal to $10.