A young couple has received a gift of $5000, which they would like to use to buy shares in a mutual fund. They are in the 15% bracket for federal income tax, and they pay no state or local income taxes. 

Should they purchase shares in a tax-free municipal bond fund that pays 4% annual interest or a high quality corporate bond fund that pays 6% interest? 

Both funds are highly recommended, and both have had similar fluctuations in price; the only difference between the two funds is that the interest from the municipal bond fund is tax deductible, whereas the higher interest from the corporate bond fund is not.