Marginal Incorporated (MI) has determined that its after-tax cost of debt is 5.0 % for the first $58 million in bonds it issues, and 8.0 % for any bonds issued above $58 million. Its cost of preferred stock is 15.0%. Its cost of internal equity is 17.0 % , and its cost of external equity is 21.0 % . Currently, the firm's capital structure has $530 million of debt, $150 million of preferred stock, and $320 million of common equity. The firm's marginal tax rate is 25%. The firm's managers have determined that the firm should have $58 million available from retained earnings for investment purposes next period. What is the firm's marginal cost of capital at a total investment 6 level of $145 million? 11.93% 13.21% 10.34% 11.62% 12.15% 10.87 % 9.68% 10.96%