A firm is considering three investment projects which we will refer to as A, B, and C. Each project has an initial cost of $10 million. Investment A offers an expected rate of return of 16%, B of 8%, and C of 12%. The firm's cost of capital is 6% if it borrows $10 million, 10% if it borrows $20 million, and 15% if it borrows $30 million. Which project(s) should the firm invest in?

A. Just A, because it offers the highest rate of return and is the only investment that has a rate of return higher than 15%
B. Only A and C should be undertaken because both have rates of return that are greater than
C. None of the above is correct.
D. All three should be undertaken, because the rate of return on B is above 6%, on C is above