Based on the following information, what is the firms weighted average cost of capital of the non-operating assets, WACC_N?

The firm:

Cost of debt, R_D: 5%

Cost of equity, R_S: 20%

Total market value of debt, D: $800

Total market value of equity, S: $800

Corporate tax rate, T: 40%

Operating assets:

Total market value, O: $1,200

Cost of debt, R_OD: 3%

Cost of equity, R_OS: 12%

a.

.218

b.

.233

c.

.199

d.

.253

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 D) .253, can you please explain how, why?