$100,000 of retained earnings in the coming year; once these retained earnings are exhausted, the firm will use new common stock as the form of common stock equity financing. a. Calculate the after-tax cost of debt. b. Calculate the cost of preferred stock. c. Calculate the cost of common stock. d. Calculate the firm's weighted average cost of capital using the capital structure boweights shown in the following table. (Round answer to the nearest 0.1%.) Source of capital Weight Long-term debt 30% Preferred stock 20 Common stock equity 50 Total 100%