Need help with question C (at what tax rate would he be indifferent between the bonds?).

Dennis is currently considering investing in municipal bonds that earn 5.55 percent interest, or in taxable bonds issued by the Coca-Cola Company that pay 7.4 percent. a. If Dennis's tax rate is 10 percent, which bond should he choose? Municipal bonds Taxable bonds b. Which bond should he choose if his tax rate is 40 percent? Municipal bonds O Taxable bonds c. At what tax rate would he be indifferent between the bonds? ax rate