Long-term debt A firm has determined its cost of each source of capital and the percentage of each source making up the firm's capital structure: Source of Capital Capital Structure Proportions 40% After-Tax Cost 6% Preferred stock 10 11 Common stock equity 50 15 The weighted average cost of capital is OA.6 percent OB. 10.7 percent OC. 11 percent OD. 15 percent