Debreu beverages has an optimal capital structure that is 70% common equity, 20% debt, and 10% preferred stock. debreu's pretax cost of equity is 9%. its pretax cost of preferred equity is 7%, and its pretax cost of debt is also 5%. if the corporate tax rate is 21%, what is the weighted average cost of capital?

Atennis club charges a monthly membership fee of $150 and charges it members $10 per hour to use a court. there's also $500 fee to become a member. stella joined the tennis club last spring, and she has been a member for 5 months. she has been playing 10 hours of tennis each month. stella values an hour of her time at $20. during a boring afternoon meeting, stella thinks about reserving a court to work on her serve for an hour tonight. what's stella's opportunity cost of working on her serve for an hour?