Source of capital Individual cost Market value $750,000 $30,000 $600,000 Long-term debt 7.8% 10.9% Preferred stock Common stock equity 14.6% WACC -Market value weights The market values and after-tax costs of various sources of capital used by Ridge Tool are shown in the following table: a. Calculate the firm's weighted average cost of capital b. Explain how the firm can use this cost in the investment decision-making process. %. (Round to two decimal places.) a. The firm's weighted average cost of capital, r, using market value weights is