3. (15 points) Consider an entry game. First the entrant decides whether to enter. Then the incumbant decides whether to undercut. Then the entrant decides whether to undercut in turn. If there is only one firm in the market they get 10. If both firms are in the market with no undercutting they get 5. If one firm undercuts they get 7 and the other firm gets 1. If both firms undercut they both get 2. Draw the extensive form of the game and find the subgame perfect equilibrium