Answer:
tax-rate 32.73%
Step-by-step explanation:
The municipal bonds are tax-free thus, the private corporate bond is a pre-tax yield. We should solve for thetax rate which makes the 6.16% private bond yield 4.11% after tax:
0.0611 x ( 1 - t ) = 0.0411
t = 1 - 0.0411/0.0611 = 0,32733224
Being taxed at 32.73% will make the investor indifferent between these two options.