THEM: hi, i'll take the hat, ball and 2 books.  YOU: i'd like the hat and one book. you''ll have ball and 3 books.  THEM: i'll give you all the books but i can't give you the hat or the ball  YOU: either the hat and book or ball and all books.  THEM: i'll give you the ball and 2 books and i take the hat and two books.  YOU: no that's bad. just give me the hat.  THEM: sorry, that's not going to happen.