Suppose that your firm has a cost of equity of 10%, cost of preferred stock of 8%, and an after-tax cost of debt of 6%. If the firm has 30% in debt, 5% in preferred stock, and 65% in equity, what is the firm's weighted average cost of capital (WACC)? Tax rate is 20%.

a.10.8%

b.7.5%

c.8.7%

d.11.4%