THEM: i would like 2 hats, 1 book, and 1 ball.  YOU: how about 2 hats and a ball?  THEM: i'll take 2 hats and a book.  YOU: can't do that - what about 2 hats and 2 balls?  THEM: how about i take 2 books, 1 hat, and you take the rest?  YOU: nope, i will give you both the hats and both the balls  THEM: can i get both hats, 1 book, and 1 ball?  YOU: no, but i guess i will do 2 hats and a book - 3 items for each of us.  THEM: i'll take 2 hats, and a book.