Error message in a simple nested formula

Hi,

I'm trying to use this formula, and the very last part of the formula doesn't work with the "IF" and "AND" condition. I get the following message error:
"The specified formula cannot be entered because it uses more levels of nesting than are allowed in the current file format".

This is the formula:

=IF(E26="Yes",IF(E21=0.375,-2.2222*(E16-2.5)+5,IF(AND(E21=0.5,E22=2),-2.1818*(E16-2.75)+5.75,IF(AND(E21=0.5,E22>2),-3*(E16-2.375)+5.75,IF(AND(E21=0.625,E22=3.125),-2.3333*(E16-3.625)+6.125,IF(AND(E21=0.625,E22>3.125),-2.875*(E16-3.25)+5.875,IF(AND(E21=0.75,E22=3.75),-1.1579*(E16-4.75)+10.5,IF(AND(E21=0.75,E22>3.75),-1.3448*(E16-4.125)+8.875))))))))

If you remove the last part of the formula, that is,
IF(AND(E21=0.75,E22>3.75),-1.3448*(E16-4.125)+8.875

and 1 parentesis the formula works....

Please, if somebody knows how to fix this, it would be greatly appreciated.

Thanks,
Cesar