Thread: After-tax real rate of interest and minimum real interest rate??

I need help on these problems like explain it, and have an equation to solve the problem please. Anything would be appreciate it thanks!

1. Assume the following;

r = 4%
τ = 0.2
π = 4%


What is the after-tax real rate of interest? ______________

1. Assume the following;

r = 4%
τ = 0.2
π = 20%

What is the after-tax real rate of interest? ______________

1. Assume a liquidity trap where i = 0% and π = 3%, what is the minimum real interest r? ___________________

1. Assume a liquidity trap where i = 0% and π = -8%, what is the minimum real interest r? ___________________

What are i, T, r, and n please specify.