Can you please tell me where I'm going wrong with my WACC calculation? Tax rate = 35%, Risk free rate = 4%, risk prem = 7%, unlevered beta = 1.5. Using the CAPM to estimate the cost of common equity and estimates that the risk-free rate is 4%, the market risk prem is 7%, and tax rate is 35%. The company estimates that if it had no debt, its "unlevered" beta would be 1.5 1) What would be the WACC at the optimal capital structure? What would teh firm's optimal capital structure be? My professor says WACC should be 13.77, but my calcuation at 60/40 is coming out to 3.836. Help please.

Debt-to-Capital Ratio	Equity-to-Capital Ratio	Debt-to-Equity Ratio	Bond Rating	Before-Tax Cost of Debt	Rate of Interest	Cost of Equity	Weighted cost of capital
(wd)	(we)	(D/E)	(rd)	((rd(1-T))		re
0.0	1.0	0.00	A	6.0%	3.9	9.425	9.425
0.2	0.8	0.25	BBB	7.0%	4.55	9.425	7.554
0.4	0.6	0.67	BBB	9.0%	5.85	9.425	5.691
0.6	0.4	1.50	C	11.0%	7.15	9.425	3.836
0.8	0.2	4.00	D	14.0%	9.1	9.425	1.997