Auto Populate

[OKCIrish]

I've been all over the internet looking for formulas to try and make a cell auto populate depending on two cells text. I am trying to have column X populate with RPR when certain texts are selected from column K & T (basically all the text in the attached picture except OK, OK-FR, UND, STS). Column X was supposed to have data validation attached to it with drop down of OK, OK-HB, RPR & DBR but I disabled it because when I found simple formulas to work with it, it wouldn't return the value due to the data validation. Does anyone know of a way to solve this? I could use the simple formula I came up with but it would be a long string of formulas.

 

[OKCIrish]

=IF(OR(K52="",T52=""),"",IF(AND(K52="ok",T52="ok"),"ok","rpr"))

The first section makes X blank if either K or T is blank. Otherwise if checks if both are "ok" (yields "ok"), else "rpr".

What would I have to do in order to add another parameter to this formula? I would like add OK-FR and if it also yields that than OK as well. I've tried adding it to the string and using more and/or functions and don't get the proper results.