Mohegan Sun is officially in the running to build a casino in Palmer.  The company has filed paperwork with the Mass Gaming Commission and submitted their $400,000 application fee.  Mohegan Sun will up against MGM, Penn National and Hard Rock International for the one casino license in the western part of the state.  Developers have until 5 p.m. today to submit applications for one of the three casino licenses to be issued statewide.