7.8 Please double check work, tutor has done it twice and given wrong answers. Not sure how to solve and get right answer. 10.86 and 10.81 both incorrect!

Looking to find WACC here.

Suppose that B2B, Inc. has a capital structure of 37 percent equity, 18 percent preferred stock, and 45 percent debt. Assume the before-tax component costs of equity, preferred stock, and debt are 15.0 percent, 12.0 percent, and 10.0 percent, respectively. What is B2B's WACC if the firm faces an average tax rate of 21 percent and can make full use of the interest tax shield? (Round your answer to 2 decimal places.)