Using IF function to designate two values into 1 group

When using IF function to make two values as one group it returns error where am i went wrong? The function is as below

IF("Class Code"=='U' AND 'P', 'Productive') I tried this also not working IF("Class Code"=='U' OR 'P', 'Productive')

It works if using only one value like so

IF("Class code"=='U', 'Productive')

Would someone be so kind to advise?

Error