Average cost for a private movie screening at a movie theatre?

I was wondering, specifically at a theatre of the Cinemark theatre chain [used to be Century Theatres], because I had the idea of having a private movie screening at the smallest theatre in size for my fifthteenth birthday party. Just one movie, and next month. How much do you think would it cost? I don't want to call in the branch and ask about it over the phone because it's just a petty thing to ask -laughs nervously-. Anyways, thanks for the answers! =]