An investor purchases one municipal bond and one corporate bond that pay rates of return of $8\%$ and $9\mathrm{.}6\%,$ respectively. If the investor is in the $20\%$ tax bracket, his after$-$tax rates of return on the municipal and corporate bonds would be$,$ respectively, $\_\_\_\_\_\_\_\_\_\_$blank.

Group of answer choices

$60\%$ and $7\mathrm{.}68\%$

$8\%$ and $7\mathrm{.}68\%$

$40\%$ and $9\mathrm{.}6\%$

$8\%$ and $9\mathrm{.}6\%$