$2.$ Marginal Incorporated $($MI$)$ has determined that its before$-$tax cost of debt is $5\mathrm{.}0\%$ for the first $$198$ million in bonds it issues, and $8\mathrm{.}0\%$ for any bonds issued above $$198$ million. Its cost of preferred stock is $11\mathrm{.}0\%.$ Its cost of internal equity is $16\mathrm{.}0\%,$ and its cost of external equity is $20\mathrm{.}0\%.$ Currently, the firm's capital structure has $$310$ million of debt, $$30$ million of preferred stock, and $$160$ million of common equity. The firm's marginal tax rate is $35\%.$ The firm's managers have determined that the firm should have $$73$ 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 $$137$ million?