Assume That Marginal Revenue Equals Rising Marginal Cost at 100

Assume that marginal revenue equals rising marginal cost at 100 units of output. At this output level, a profit-maximizing firm's total fixed cost is $600 and its total variable cost is $400. If the price of the product is $3 per unit and the firm produces at the profit-maximizing level, the firm will earn an economic profit equal to

A) $1,000.
B) $700.
C) $400.
D) $600.
E) -$700.