I believe that a Response Pad Xr (Xrc-01) is mandatory for a couple of my classes. When I typed that into amazon it was much cheaper than the SUPeStore sells it for. Does anybody know if it would be ok to purchase it off amazon, I am really not even sure what it is. Also I am having a hard time deciphering which textbooks are mandatory and which ones are not,(most of my books do not say optional or required.) Does any body have any advice on that, or should I just wait until the first week of school to purchase my books?