Physics Question regarding work and bananas?

You have just slid a banana box full of Physics books off the table in the back of the room. You hold them at that same height while you take them to the library, which is on the same floor and you place them on the same kind of table to took them from. You comment to the librarian that it was a lot of work. The cl Physics geek hears you and says you didn't do any work. Explain.