An investor is considering a muni bond paying $3\mathrm{.}47\%$ and an investment grade corporate bond paying $5\mathrm{.}18\%.$ At what tax rate would they be indifferent between the two bonds? State your answer as a percentage with two decimal places and not in decimal form itself $($i$.$e$.13\mathrm{.}21$ not $\mathrm{.}1321).$