Marginal Incorporated (MI) has determined that its before-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 level of $76 million