Olsen Outfitters Inc. believes that its optimal capital structure consists of 70% common equity and 30% debt, and its tax rate is 40%. Olsen must raise additional capital to fund its upcoming expansion. The firm will have $2 million of retained earnings with a cost of r_s = 10%. New common stock in an amount up to $10 million would have a cost of r_e = 13.0%. Furthermore, Olsen can raise up to $3 million of debt at an interest rate of r_d = 9% and an additional $5 million of debt at r_d = 12%. The CFO estimates that a proposed expansion would require an investment of $6.0 million. What is the WACC for the last dollar raised to complete the expansion?