Sorensen Systems Inc. is expected to pay a $2.50 dividend at year end (D1=$2.50), the dividend is expected to grow at a constant rate of 5.50% a year, and the common stock currently sells for $87.50 a share. The before-tax cost of debt is 7.50%, 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. 6.99% b. 7.21% c. 5.98% d. 7.13% e. 6.85%