A perfectly competitive firm, earning economic profits, produces and sells 100 units of output at a price of $20 per unit. If its marginal cost of increasing output to a rate of 101 units is $18, which of the following statements is correct

A. the total revenue from selling 101 units is the same as the total revenue from selling 100 units.
B. the total profit from selling 101 units is $2 greater than the total profit from selling 100 units.
C. the total cost of producing 101 units is $2 greater than the total cost of producing 100 units.
D. to sell 101 units, the firm must reduce its price below $20. (E) to sell 101 units, the firm must raise its price above $20.