Marginal Incorporated $($MI$)$ has determined that its after$-$tax cost of debt is $4\mathrm{.}0\%$ for the first $$48$ million in bonds it issues, and $8\mathrm{.}0\%$ for any bonds issued above $$48$ million. Its cost of preferred stock is $12\mathrm{.}0\%.$ Its cost of internal equity is $17\mathrm{.}0\%,$ and its cost of external equity is $20\mathrm{.}0\%.$ Currently, the firm's capital structure has $$285$ million of debt, $$65$ million of preferred stock, and $$150$ million of common equity. The firm's marginal tax rate is $35\%.$ The firm's managers have determined that the firm should have $$63$ 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 $$50$ million?

$10\mathrm{.}52\%$

$12\mathrm{.}12\%$

$11\mathrm{.}22\%$

$9\mathrm{.}84\%$

$8\mathrm{.}94\%$

$9\mathrm{.}62\%$

$8\mathrm{.}14\%$

$9\mathrm{.}04\%$