Given the following information, calculate the firm's weighted average cost of capital (WACC). Market value of common stock=$60 million; market value of preferred stock=$10 million, market value of debt=$30 million; cost of common stock=15%; cost of debt=10%; tax rate=40%. The preferred stock pays a constant $4 dividend and is now selling for $50 a share.
A. 11.60%
B. 12.60%
C. 12.97%
D. 13.32%