Consider the following two-player game. First, player 1 selects a number x 0. Player 2 observes x. Then, simultaneously and independently, player 1 selects a number y₁ and player 2 selects a number y₂, at which point the game ends.

Player 1's payoff is: u₁(x, y₁) = 3y₁² + 6y₁y₂ 8xy₂.

Player 2's payoff is: u₂(y₂) = 3y₂ + 6y₁y₂ 6y₂² + 12xy₂.

Draw the game tree of this game and identify its Subgame Perfect Nash Equilibrium.