An investor purchases one municipal and one corporate bond that pay rates of return of 6% and 8%, respectively. If the investor is in the 25% marginal tax bracket, his or her after-tax rates of return on the municipal and corporate bonds would be ________ and ______, respectively.

A. 6%; 8% B. 4.5%; 8% C. 6%; 6% D. 4.5%; 6%