a. The ball's horizontal and vertical positions at time
are given by


The ball reaches the net when
:

At this time, the ball is at an altitude of

which is 1.40 m - 0.900 m = 0.500 m above the net.
b. The change in angle gives the ball the new position functions


The ball reaches the net at time
such that

at which point the ball's vertical position would be

so that the ball does not clear the net with 0.343 m - 0.900 m = -0.557 m.