THEM: can i get two balls, 1 book and a hat?  YOU: i need both balls and either 1 hat or 1 book.  THEM: you can have one ball and i'll take everything else  YOU: no deal. i can do 1 ball and the 3 books or 1 ball, 1 hat and 2 books.  THEM: no deal. i need one ball and at least two books. you can have the hat  YOU: fine. you take 1 ball and 2 books. i'll take the rest.