A firm issues a $20-$year semi$-$annual coupon payment bond, which nets it $$1,313\mathrm{.}55.$ The coupon rate of the bond is $9\mathrm{.}00\%.$ The tax rate is $21\%.$ What is the after$-$tax cost of debt?

A$.8\mathrm{.}99\%$

B$.7\mathrm{.}91\%$

C$.6\mathrm{.}99\%$

D$.6\mathrm{.}21\%$

E$.5\mathrm{.}53\%$

F$.4\mathrm{.}93\%$

G$.4\mathrm{.}38\%$

H$.3\mathrm{.}90\%$