what is New York Key’s weighted marginal cost of capital

New
Your Key is planning a $50 million expansion. The expansion is to be
financed by selling $20 million in new debt and $30 million in new
common stock. The before-tax required rate of return on debt is 9%, and
the required rate of return on equity is 13.75%. If the company is in
the 40% tax backed, what is New York Key’s weighted marginal cost of
capital?

a. 7.5%
b. 9.2%
c. 10.4%
d. 13.8%