Marginal Incorporated $($MI$)$ has determined that its after$-$tax cost of debt is $5\mathrm{.}0\%$ for the first $$62$ million in bonds it issues, and $7\mathrm{.}0\%$ for any bonds issued above $$62$ million. Its cost of preferred stock is $12\mathrm{.}0\%.$ Its cost of internal equity is $15\mathrm{.}0\%,$ and its cost of external equity is $19\mathrm{.}0\%.$ Currently, the firm's capital structure has $$325$ million of debt, $$70$ million of preferred stock, and $$105$ million of common equity. The firm's marginal tax rate is $45\%.$ The firm's managers have determined that the firm should have $$50$ 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 $$167$ million?

$8\mathrm{.}08\%$

$10\mathrm{.}22\%$

$9\mathrm{.}38\%$

$8\mathrm{.}92\%$

$8\mathrm{.}17\%$

$7\mathrm{.}33\%$

$6\mathrm{.}62\%$

$7\mathrm{.}46\%$