A firm has a target capital structure of 30% debt, 20% preferred stock, and 50% common equity. The company's before-tax cost of debt is 5%, its cost of preferred stock is 8%, and its cost of retained earnings is 12%. The firm's marginal tax rate is 21%. What is the company's weighted average cost of capital if retained earnings are used to fund the common equity portion? 8.0% 9.50% 9.10% 8.79%