The Diagram Below Shows the Marginal Cost of Abatement for Each

The diagram below shows the marginal cost of abatement for each of two firms, A and B. Each firm is initially abating Q0 units of pollution. FIGURE 17- 6
-Refer to Figure 17- 6. Suppose that a system of tradable pollution permits is introduced into this market and the equilibrium permit price is p×. Firm A will sell permits to Firm B because

A) Firm B has lower costs of pollution abatement than Firm A.
B) the revenue Firm A earns from selling permits (areas 5 + 6) is greater than the cost it incurs from abating more pollution (area 6) .
C) Firm A can buy the permits at a lower price than Firm B.
D) Firm A's total cost of abating more pollution (area 6) is less than the revenue it earns from selling the permits (areas 4 + 5) .
E) Firm A's total cost of abating more pollution (areas 5 + 6) is less than the revenue it earns from selling the permits (areas 4 + 5 + 6) .