LO $4-619.$ Mr$.$ Fuentes has $$15,000$ to invest. He is undecided about putting the money into tax$-$exempt municipal bonds paying $3\mathrm{.}5$ percent annual interest or corporate bonds paying $4\mathrm{.}75$ percent annual interest. The two investments have the same risk.

a$.$ Which investment should Mr$.$ Fuentes make if his marginal tax rate is $32$ percent?

b$.$ Would your conclusion change if Mr$.$ Fuentes's marginal tax rate is only $12$ percent?