THEM: i'd like one of each kind of item. you can have the remaining three books.  YOU: no. i'd like hat and ball.  THEM: yes, they are nice. i'd like them also. i can let you have all 4 books.  YOU: that's only 4 points. i can do all 4 books and the ball or the hat and 2 books.  THEM: how about i get the ball and three books, you get the hat and the other book.  YOU: have to have two books with the hat.  THEM: deal.