I use a spreadsheet to track loads of corn to the elevator.  Each load shows what it costs to dry and store. 

This year the elevator has a 3 tiered price for drying.  In the past I only had to contend with 2 prices.

 IF(B7>=15,IF(B7>=20.1,(0.045*(B7-15))*A7,(0.04*(B7-15)*A7)),0)

The above formula worked fine when I only had the 2 prices. 

B7 being the cell with the moisture and A7 being the cell with the wet bushels.

Their current pricing is;

15.1% to 20.0%   $.04

20.1% to 23.0%   $.045

23.1% to 28.0%   $.05

I've had no success writing a formula for the third pricing.  I think the first IF statement limits me to 2 options.  I've heard people mention a lookup table but I haven't the knowledge as to how to implement one.  

Help would be greatly appreciated.