Any difference between WACC and MCC difference, discount, question, required

ikoreaii

Hi guys, just want to check if WACC and MCC are both the same thing?

In the kaplan notes under LOS 45b, it state that the discount rate is the firm's weighted average cost of capital (WACC) and is also referred to as the marginal cost of capital (MCC).

I have this question from the 2009 CFA mock exam:

a company optimal capital budget is best described as the amount of new capital required to undertake all projects with an internal rate of return greater than the:
a) marginal cost of capital
b) cost of new debt capital
c) weighted average cost of capital

the correct ans is a. Just like to confirm if wacc is mcc. If it is, how does this theory apply to this question?

thanks