They should tell you this as a group at some point in the day. I would tread lightly with this question - programs want you to be interested in the time you spend at work, not in how much time you'll spend away from it.
"Trickiest" questions I've been asked so far have been: "tell me about a book you recently read", "tell me something about yourself that is not mentioned in your application materials", and "tell me about your relationship with your father".