THEM: i'd like the book and the three hats.  YOU: you can have the hats but, i need the book and the ball  THEM: sorry i need the book. you can have the ball and two hats.  YOU: i can not make that deal. we both need the book so we will not be able to reach a deal.  THEM: what if you keep everything but the book?  YOU: it still would not work out for me. i'm sorry.  THEM: ok. take the book. i'll keep the three hats and the ball.  YOU: okay deal.