My professors answer for this is WACC is 11.73% I need to know how he got it, abse of the BERKSHIRE INSTRUMENTS CASE 16 CHAPTER 11 -COST OF CAPITAL. THANK YOU.

Determine the weighted average cost of capital based on using retained earnings in the capital structure. The percentage composition in the capital structure for bonds, preferred stock, and common equity should be based on the current capital structure of long-term financing as shown in Figure 1 (it adds up to $18 million). Common equity will represent 60 percent of financing throughout this case.