An investor purchases one municipal bond and one corporate bond that pay rates of return of 8% and 9.6%, respectively. If the investor is in the 20% tax bracket, his after-tax rates of return on the municipal and corporate bonds would be, respectively, _____.

a.8% and 9.6%

b.8% and 7.68%

c.6.40% and 9.6%

d.9.60% and 7.68%