Please provide a written out by hand solution for the above example.

1.4) A firm's stockholders expect a 15% rate of return, and there is $12M in common stock and retained earnings. The firm has $5M in loans at an average rate of 7%. The firm has raised $8M by selling bonds at an average rate of 6%. What is the firm's cost of capital after tax with a tax rate of 35%? a. 9.4% b. 9.8% c. 6.8% d. 10.5%