Olsen Outfitters Inc. believes that its optimal capital structure consists of $45\%$ common equity and $55\%$ debt, and its tax rate is $25\%.$ Olsen must raise additional capital to fund its upcoming expansion. The firm will have $$1$ million of retained earnings with a cost of $r_s=11\%.$ New common stock in an amount up to $$8$ million would have a cost of $r_e=13\mathrm{.}0\%.$ Furthermore, Olsen can raise up to $$3$ million of debt at an interest rate of $r_d=11\%$ and an additional $$3$ million of debt at $r_d=15\%.$ The CFO estimates that a proposed expansion would require an investment of $$4\mathrm{.}0$ million. What is the WACC for the last dollar raised to complete the expansion? Round your answer to two decimal places.

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