The game tree

Challenger firm C is considering entry into a market that is currently occupied by an incumbent monopolist M. If C stays out, it earns $0 in profits while M earns monopoly profits $20 million. If C enters, it incurs entry costs and must also consider a possibility of M starting a price war. If M starts a price war, M’s profits fall to $5 million while C incurs a loss of -$2 million. If M does not start a price war upon C’s entry, each firm earns $7 million.
i. Assume that firm C moves first. Draw the game tree. (4 marks)
ii. What is the Subgame Perfect Nash Equilibrium of this game? Is M’s promise to start a price war a credible threat? (9 marks)