Formula for commission report

Hi,
I wonder if someone could help me please?

I am trying to design a commission report that will automatically calculate total commissions, based on revenue by a multplier.
Essentially 1-3 contracts they get paid x 1 on the total revenue, 4-6 they get paid x 2 and 7+ x3.

I want each contract name to be listed and the revenue to be inputted, but for it then to automatically select the correct multiplier from the number of contracts entered and multiply it by the total revenue. I'm struggling with a way for it to identify the correct multiplier.

Many thanks for any help you can give me!

Julia