Debreu Beverages has an optimal capital structure that is 70% common equity, 20% debt, and 10% preferred stock. Debreu's pre-tax cost of equity is 9%. Its pre-tax cost of preferred equity is 7%, and its pre-tax cost of debt is also 5%. If the corporate tax rate is 35%, what is the weighted average cost of capital?
A) Between 7% and 8%
B) Between 8% and 9%
C) Between 9% and 10%
D) Between 10% and 12%