I need a formula to to set the following 4 text values in a cell (B1) based on a range of numbers entered in another cell (A1):

Text value "Small" if number entered is less than 8.
Text value "Medium" if number entered is between 9 and 15 (inclusive).
Text value "Large" if number entered is between 16 and 20 (inclusive).
Text value "Error" if number entered is greater then 20.

Can anyone help please? It's driving me nuts!

Thanks,
Osmer