THEM: i want the books and hat  YOU: i want both books and a ball  THEM: i'll trade you a hat for a book, so two books and one ball for me  YOU: no can do. if i am getting the hat i need one book and one ball also  THEM: how about i take both books and give you the rest?  YOU: can't do it.. i need at least one book in which case i need the hat and one ball as well  THEM: then no deal  YOU: the only other deal is for me to take both books and give you all else  THEM: can't do it  YOU: ok no deal.