A firm has determined its cost of each source of capital and optimal capital structure, which is composed of the following sources and proportions: Source of Capital Proportions After-Tax Cost Long-term debt 4000 696 Preferred stock 10 11 Common stock equity 50 15 The weighted average cost of capital is: A 6% B. 10.7% C 119 D 15% O 6% 10.7% 11% 15%