A firm$$s bondholders are earning a $7\mathrm{.}5\%$ return and the firm$$s stockholders are earning a $15\%$ return. The firm$$s financing is $35\%$ debt and $65\%$ equity. The firm$$s average tax rate is $27\%.$

What is the firm$$s after$-$tax cost of debt?

Group of answer choices

$2\mathrm{.}5\%$

$3\mathrm{.}5\%$

$4\mathrm{.}5\%$

$5\mathrm{.}5\%$

$6\mathrm{.}5\%$

$7\mathrm{.}5\%$

$15\%$