Need some help please. I have a rate chart that if a cubic foot falls within a range then i can bill a certain amount.

Example

0-20 = $2.99

21-40 = $2.67

41-60 = $2.41

This is based on cubic footage of a box which is calculated and placed in a cell so if the cubic footage is 6.12 CFT then i need something to be able to look at a table and read that as the CFT falls between 0-20 then it will be $2.99 multiplied by the CFT (which is 6.12) totaling $18.29

L | W | H | CFT | RATE | COST |

21 | 21 | 24 | 6.12 | 2.99 | 18.29 |

<tbody>

</tbody>

I have 8 ranges that i calculate and manually punch this info into our system and i would love something that recognises that the CFT would fall between a certain range and then calculate the correct rate and then final cost

Please be gentle with me if im posting where i shouldn't as this is my first time posting