If Greater than or small than, or equal to

Hi everyone,

I am not sure how to do this, I hope you can help.

I have a cell, M87.

The score in M87 can be less than 13 or greater than 25

I need a formula within M94 which refers to M87, and outputs depending on the the following criteria

If M87 is less than 13 then output as D

If M87 is 14, 15, 16, or 17 then output as C

If M87 is 18, 19, 20, 21, 22, 23 or 24 then output as B

If M87 is greater than 24 then output as A.

I hope you can help me with this formula.

I look forward to hearing from you.

Ravi