3.90 was incorrect for the cost of debt, please help!

Ninecent Corporation has a target capital structure of 60 percent common stock, 5 percent preferred stock, and 35 percent debt. Its cost of equity is 10 percent, the cost of preferred stock is 5 percent, and the pretax cost of debt is 6 percent. The relevant tax rate is 22 percent. a. What is the company's WACC? (Do not round intermediate caiculations and enter your answer as a percent rounded to 2 decimal places, e.9., 32.16.) b. What is the aftertax cost of debt? (Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)