Carter Corporation Has Some Money to Invest, and Its Treasurer

Carter Corporation has some money to invest, and its treasurer is choosing between City of Chicago municipal bonds and U.S. Treasury bonds. Both have the same maturity, and they are equally risky and liquid. If Treasury bonds yield 6 percent, and Carter's marginal income tax rate is 40 percent, what yield on the Chicago municipal bonds would make Carter's treasurer indifferent between the two?

A) 2.40%
B) 3.60%
C) 4.50%
D) 5.25%
E) 6.00%