Actual After-Tax Rate of Return.

Greetings,

I'm trying to solve a 3 part problem which has the following questions:

**a)** Determine the rate of return before taxes.

**After Solving: Answer: 21 %**

**b) **If the effective income tax rate is 42 percent, what is the approximate after-tax rate of return?

**After Solving: Answer: 8 %**

**c) **What is the actual after-tax rate of return?

**I don't really understand this question, I can't tell the difference between (approximate after-tax rate of return) and (actual after-tax rate of return)**

Does anyone Know the difference?

thanks.