Acme Co. has a capital structure, based on current market values, that consists of 50 percent debt, 10 percent preferred stock and 40 percent common stock. If the returns required by investors are 8 percent for the debt, 10 percent for the preferred stock and 15 percent for the common stock, what is Acme's after tax weighted average cost of capital. Assume that the firm's marginal tax rate is 40 percent.