You were hired as a consultant to Giambono Company, whose target capital structure is $40\%$ debt, $15\%$ preferred, and $45\%$ common equity. The after$-$tax cost of debt is $6\mathrm{.}00\%,$ the cost of preferred is $7\mathrm{.}50\%,$ and the cost of retained earnings is $16\mathrm{.}00\%.$ The firm will not be issuing any new stock. What is its WACC?

a$.$

$10\mathrm{.}94\%$

b$.$

$8\mathrm{.}26\%$

c$.$

$8\mathrm{.}69\%$

d$.$

$13\mathrm{.}41\%$

e$.$

$10\mathrm{.}73\%$