A company has debt outstanding with a market value of $100 million, and equity outstanding with a market value of $700 million. It is in the 24% tax bracket, and its debt is considered risk free. According to an investment bank, its equity beta is 1.50. Given a risk-free rate of 2% and an expected market return of 10%, calculate the discount rate for a scale enhancing project in the hypothetical case that it is all-equity financed.

how to calculate r_b (required return on corporate debt) ?

and is the question asking to calculate r_wacc out?