Waller, Inc., is trying to determine its cost of debt. It issued a $15-$year, $8\%$ coupon, semiannual bond $3$ years ago. The bond is currently quoted at $94\%$ of face value. If the tax rate is $37\%,$ which of the following is closest to the after$-$tax cost of debt? $($Do not round your intermediate calculations.$)$

Question $6$ options:

$8\mathrm{.}72\%$

$5\mathrm{.}56\%$

$5\mathrm{.}50\%$

$4\mathrm{.}41\%$