Sorensen Systems Inc. is expected to pay a $$2\mathrm{.}50$ dividend at year end $(($:$D_1=$$$2\mathrm{.}50\},$ the dividend is expected to grow at a constant rate of $5\mathrm{.}50\%$ a year, and the common stock currently sells for $$87\mathrm{.}50$ a share. The before$-$tax cost of debt is $7\mathrm{.}50\%,$ and the tax rate is $25\%.$ The target capital structure consists of $45\%$ debt and $55\%$ common equity. What is the company's WACC if all the equity used is from retained earnings? Do not round your intermediate calculations.

a$.5\mathrm{.}98\%$

b$.6\mathrm{.}85\%$

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

d$.7\mathrm{.}21\%$

e$.7\mathrm{.}13\%$