Thanks to those who "liked" the app. I was able to submit it last week. It took a few days for FB to approve it, then several more days for it to appear in the application directory.
The FB version is exactly the same as the normal one (actually the same place except FB contains a window with the site in it).
http://apps.facebook.com/rc_calculations/
In the future, I will be looking into making the page look prettier, but it'll work for now...