Calculating Marginal Cost of Capital

A company is assessing its cost of capital and wants to determine its marginal cost of capital (MCC) as it considers an additional project. The firm currently has a mix of financing from equity and debt, with a recent issuance of equity at a cost of 8% and debt issued at a cost of 5%. They plan to finance new investments partly with retained earnings and partly with a new debt offering.

What would be the marginal cost of capital for the next dollar raised if the new debt is issued at a rate of 6%? Consider the weighted average cost of capital (WACC) principles in your answer.