

![0_image_0.png](0_image_0.png)

is a win for X if X is on play. 4  So is and the tree can be reduced to: where it is O's turn as opposed to X's. If O moves in the second row, we get an instance of
$\mathbf{M}$
 $\blacksquare$
(3)

We get $\mathrm{a}$. 
(4)
while if O moves to the upper right, we get an instance of