1)- A municipal bond selling at par currently yields 7.5%. A corporate bond selling at par currently yields 10%. At what marginal tax rate would an investor be indifferent between this two bonds?

2)- A corporate bond selling at par currently yields 7.5%. Amy's marginal tax rate is 20%. How much should a municipal bond selling at par yields so that Amy is indifferent between this two bonds?

3)- A municipal bond selling at par currently yields 6.5%. Bob's marginal tax rate is 20%.How much should a corporate bond selling at par yields so that Bob is indifferent between this two bonds?