You were hired as a consultant to Giambono Company, whose target capital structure is 40% debt, 15% preferred, and 45% common equity. The after tax cost of debt is 6.00%, the cost of preferred is 7.50%, and the cost of retained earnings is 11.50%. The firm will not be issuing any new stock. What is its WACC? Select one: O a. 8.87% b. 766% O c. 6.70% O d. 7.92% O e. 8.70%