stats coursework help (in Off-topic)

stck on one question anyone got any ideas on how to go about it?
Discuss, with supporting calculations:
(ii)ﾓOur financial planning model reveals that the mean profit before tax is ﾣ4.6m, the standard deviation of the profit before tax is ﾣ3.5m, interest paid is ﾣ1.0m and the tax on profit after interest is 30%. However, the standard deviation of the profit after interest and tax is still ﾣ3.5m, because the interest and the tax rate are both constant.ﾔ

There really are no calculations for this problem.

You know that the mean profit after tax is the mean profit before tax subtracted by the tax and the interest.

So really, the model for the profit AFTER tax is just the model for the profit BEFORE tax shifted down.

I guess you can think of it this way:

If I have somewhere between 20-40 apples, and you steal 10 of them, I know that I have somewhere between 10-30 apples, not 15-25 apples or something like that.