Assume that John Richards pays income taxes at a 30 percent rate. He currently owns a not-for-profit (municipal) bond that pays 5 percent interest. What interest rate would have to be set on a for-profit (corporate) bond to produce the same amount of usable (after-tax) income? a. 5.0% b. 5.7% c. 6.6% d. 7.1% e. 8.4%