MCC

I am a little confused on how to calculate this. I am referring to question 22 of Reading 45 from the CFAI textbook. The way I understand it, MCC is the marginal cost. Therefore, it should be the cost of issuing the new equity only. The company is not planning to issue more debt, so I don’t understand why we want to calculate the WACC in this case. Thanks for any help.

Nevermind, I misunderstood what the question is asking