You live in a country with a flat, across$-$the$-$board tax of $21\%$ on all income except for the interest on a class of tax$-$exempt municipal bonds. You observe that the yield on a particular taxable corporate bond is $2\mathrm{.}70\%.$ If this is the case, what must be the yield on tax$-$exempt municipal bond with all of the same risk characteristics so that the after$-$tax returns on the two bonds are in equilibrium?

Group of answer choices

$3\mathrm{.}42\%$

$1\mathrm{.}78\%$

$2\mathrm{.}69\%$

$2\mathrm{.}24\%$

$2\mathrm{.}13\%$