Suppose Stock A (see the above question) is the equity of a company that has a target capital structure of 75% common stock and 25% debt. Using the Capital Asset Pricing Model (CAPM), you have determined that its cost of equity is 9.90%. Stock A is able to borrow at a pre-tax cost of debt of 4.50%, and its tax rate is 25%. 

Calculate the weighted average cost of capital (WACC) of this company.