Wentworth's Five and Dime Store has a cost of equity of $11\mathrm{.}5$ percent. The company has an aftertax cost of debt of $5\mathrm{.}1$ percent, and the tax rate is $21$ percent. If the company's debt$-$equity ratio is $\mathrm{.}75,$ what is the weighted average cost of capital?

Multiple Choice

$7\mathrm{.}90\%$

$8\mathrm{.}76\%$

$7\mathrm{.}42\%$

$6\mathrm{.}81\%$

$6\mathrm{.}71\%$