Sheridan Co. has a capital structure, based on current market values, that consists of 45 percent debt, 6 percent preferred stock, and 49 percent common stock. If the returns required by investors are 8 percent, 10 percent, and 15 percent for the debt, preferred stock. and common stock, respectively, what is Sheridan's after-tax WACC? Assume that the firm's marginal tax rate is 28 percent. (Do not round intermediate calculations. Round answer to 1 decimal place, eg. 15.2\%.) After tax WACC