6.1 Draw a game tree that represents the ultimatum game in which the proposer is a first mover who decides how much to offer a responder and the responder then decides to accept or reject the offer.

The total amount available is $50 if the players reach agreement, but both players get nothing if the responder rejects the offer. The proposer is allowed to make an offer of $5, $15, $25, $35, or $45. What is the subgame-perfect Nash equilibrium? What would you expect to happen in practice?