Schadler Systems is expected to pay a $$2\mathrm{.}20$ dividend at year end $($D$1),$ the dividend is expected to grow at a constant rate of $6\mathrm{.}50\%$ a year, and the common stock currently sells for $$64\mathrm{.}00$ a share. The before$-$tax cost of debt is $7\mathrm{.}00\%,$ and the tax rate is $47\%.$ The target capital structure consists of $41\%$ debt and $59\%$ common equity. What is the company's WACC if all equity is from retained earnings?

a$.7\mathrm{.}38\%$

b$.7\mathrm{.}88\%$

c$.8\mathrm{.}73\%$

d$.4\mathrm{.}63\%$