Can someone please tell me that whether I can use fx-991 es or not? I have been using fx-991es from the past two years and I'm addicted to it

My math prof. told the class that as long as it's a Casio fx-991 (the letters don't matter can be ms or es).

should be fine. the only course that ever stated you could ONLY use the 991-MS was chem 1AA3 last year. every other course was totally fine with it (i even asked some of the profs).