Debreu Beverages has an optimal capital structure that is 70% common equity, 20% debt, and 10% preferred stock. Debreu's pretax cost of equity is 9%. Its pretax cost of preferred equity is 7%, and its pretax cost of debt is also 5%. If the corporate tax rate is 21%, what is the weighted average cost of capital?

A) Between 7-8 % B) Between 8 -9% C) Between 9-10% D) Between 10-12%