THEM: i need the books and you can have the rest  YOU: i need one book, and i'll give you a hat  THEM: i have to have both books  YOU: i can't give you both  THEM: then we can't make a deal  YOU: i think you can make due with one book and one hat  THEM: no the hats and balls have no value to me  YOU: it's better than zero value at all.  THEM: no, i neither need both books or nothing  YOU: okay have both books.