I am looking to create a formula that will allow me to calculate my example below:

First 5,000*1.6
Next 5,000*1.2
Over 10,000*1

For example the Limit entered was 15,000 the formula would have to do something like this.

5000*1.6 = 8000
5000*1.2 = 6000
5000*1 = 5000
=8000+6000+5000
=19,000

I would imagine I need to use IF statements but I just can't seem to get the result I need.