Hello, please show work if you can. Thank you!

You are choosing between buying bonds from the Rock Corporation which yield 8.4% per year, and state of Nevada local bonds which yield 4.2% per year. - For these two bonds, the break-even income tax rate for its investors equals \%. Fill out all digits, and put "O" for any blank values. - If your income tax rate is 50%, and you have no other information that could be used to make your decision, which bonds will you choose? Your