The Diagram Below Shows Selected Cost and Revenue Curves for a Firm

The diagram below shows selected cost and revenue curves for a firm in a monopolistically competitive industry. FIGURE 11-4
-Refer to Figure 11-4.Assuming this firm is producing its profit-maximizing level of output,what are the profits or losses being earned by this firm?

A) $0 per unit
B) $7 per unit
C) $13 per unit
D) $6 per unit
E) $20 per unit