Answer:
D.
Municipal bond because the equivalent taxable yield is 6.6%
Explanation:
we should make the important difference that municipal bonds are tax free while corporate bonds don't.
Therefore we should solve for the after tax rate fo the corporate bond:
[tex]pretax (1-t) = after tax -rate\\0.0625(1-0.28) = 0.0625(0.72) = 0.045[/tex]
The corporate bond as a yield of 4.5% after taxes which is lower than the municipal bond. This make it more attractive
We can also solve for the pre-tax rate of the municipal bond:
[tex]pretax(1-t) = after tax - rate\\pretax (1-0.28) = 0.0475\\pretax = 0.0475/0.72 = 0,065972 = 0.066[/tex]
the municipal bonds would be equivalent to a 6.6% corporate bonds.
This makes option D correct.