A firm has determined its cost of each source of capital and optimal capital structure, which is composed of the following sources and proportions: Proportions After-Tax Cost Source of Capital Long-term debt 40% Preferred stock Common stock equity The weighted average cost of capital is: A 6% B. 10.7% 6% 10.7% 11% C. 11% D. 15% 15% 10 50 6% 11 15