The capital structure of a firm is as follows: the tax rate is 42 percent. What is the after tax cost of capital of the firm? a. 5.51% b. 9.00% c. 8.66% d. 9.5% Solution WACC = {[(Weight of Equity x Cost of Equity)] + [(Weight of Debt x Cost of Debt) x (1 - Tax rate)]} => [(0.75 x 0.10)] + [(0.25 x 0.08) x (1 - 0.42)] = 0.075 + 0.0116 = 0.0866 or 8.66% So, option C is correct..