If the tax rate is 40 percent, compute the before tax real interest rate and the after-tax

Question:

If the tax rate is 40 percent, compute the before tax real interest rate and the after-tax real interest rate in each of the following cases.
a. The nominal interest rate is 10 percent, and the inflation rate is 5 percent.
b. The nominal interest rate is 6 percent, and the inflation rate is 2 percent.
c. The nominal interest rate is 4 percent, and the inflation rate is 1 percent