I'm not seeing the typical expensive effects like indirect lighting, soft shadows, fluids etc so this frame shouldn't be 10 minutes on a decent PC. What are your machine specs? Are you using Maya 2016? I remember borderline ripping my hair out (and finding another renderer) because mental ray's performance tanked horribly in Maya 2016. You could probably optimize the scene a bit as well. If you feel comfortable sharing the scene, you can upload it to a file sharing site and pm me the link and I'll take a look.