Can you please provide the explanation, formula and correct answer for the problem above?

I need specific step by step on how to solve the problem. The answer is B) .168751, can you please explain how/why?

Based on the following information, what is the firm's weighted average cost of capital of the operating assets, WACC ? Cost of debt, RD:7% Cost of equity, RS:20% Total market value of debt, D: 500 Total market value of equity, S:1,500 Number of common shares outstanding: 100 Total market value of non-operating assets, N:200 Cost of non-operating assets, RN:9% Corporate tax rate, T: 40% a. 127767 b. 168751 C. .143009 d. 188232 Based on the following information, what is the firm's weighted average cost of capital of the operating assets, WACC ? Cost of debt, RD:7% Cost of equity, RS:20% Total market value of debt, D: 500 Total market value of equity, S:1,500 Number of common shares outstanding: 100 Total market value of non-operating assets, N:200 Cost of non-operating assets, RN:9% Corporate tax rate, T: 40% a. 127767 b. 168751 C. .143009 d. 188232