You were hired as a consultant, and you were provided with the following data: Target capital structure: 40% debt, 10% preferred, and 50% common equity. The after-tax cost of debt is 4.00%, the cost of preferred is 7.50%, and cost of retained earnings is 11.50%. The firm will not be issuing any new stock. What is the firm's WACC? Please show work.

a. 7.55%

b. 7.73%

c. 7.94%

d. 8.10%

e. 8.32%