Answer:
The after-tax rate for the Corporate Bond when the tax rate is 10% is 9.35%
Explanation:
The investor is better of at any rate above 30%, i.e 31% of tax rate would give the investor 7.1691% return ( 10.39 − ( 10.39 ⋅ 31 % ) )
Thus the return from the tax exempt municipal bond would be higher than the return from the taxable corporate bond.
The after-tax rate for the Corporate Bond when the tax rate is 10% is 9.35%( 10.39 − ( 10.39 ⋅ 10 % ) )