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 million. 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? [ ]

please show work and formula thanks