American Airlines currently has no debt and an equity cost of capital of 15%. Suppose that American decides to increase its leverage and maintain a market debt-to-value ratio of 1/2. Suppose American's debt cost of capital is 9% and its corporate tax rate is 25%. Assuming that American's pre-tax WACC remains constant, then with the addition of leverage its effective after-tax WACC will be closest to: Select one: A. 13.88% B. 12.9% C.15.0% D.13.09