A firm's target capital structure is $50\%$ debt, $10\%$

preferred, and $40\%$ common equity. The after$-$tax cost

of debt is $5\mathrm{.}5\%,$ the cost of preferred stock is $8\mathrm{.}50\%,$ and

the cost of retained earnings is $13\mathrm{.}5\%.$ The firm will not

be issuing any new stock. What is the firm's WACC?

$9\mathrm{.}31\%$

$9\mathrm{.}78\%$

$9\mathrm{.}50\%$

$9\mathrm{.}00\%$