If a taxpayer in the 28% tax bracket has the opportunity to invest in a taxable corporate bond that pays 6% interest or to invest in a tax-exempt municipal bond that pays 3.5% interest (assuming that all other elements of the two bonds, e.g., risk, are equal and that taxable interest would not put the taxpayer in a higher tax bracket), which investment (without considering any effect of state and local taxes) would generate the greater after-tax yield?