A company has outstanding debt with a market value of 350 million, preferred stock with a market value of 100 million and common stock with a market value of 450 millions. Debt, preferred stock and equity are listed on the balance sheet for 400 million, 80 million and 250 million, respectively. If its debt has a before-tax cost of 6%, a before-tax cost of 4% for preferred stock, a before-tax cost of equity of 12% and a corporate tax rate of 30%, what is the WACC that this firm should use to evaluate average risk projects?