Solve the Problem $32 \mathrm {~m} / \mathrm { sec }$

Solve the problem.
-A rock is thrown vertically upward from the surface of the moon at a velocity of $32 \mathrm {~m} / \mathrm { sec }$ . The graph shows the height $y$ of the rock, in meters, after $x$ seconds. Estimate and interpret the turning point (the point at which the graph reaches its maximum value) .

A) The turning point is at approximately $( 40,320 )$ . This is the point at which the rock reaches its maximum height and starts to fall back towards the surface of the moon.
B) The turning point is at approximately $( 20,320 )$ . This is the point at which the rock reaches its maximum height and starts to fall back towards the surface of the moon.
C) The turning point is at approximately $( 40,0 )$ . This is the point at which the rock reaches the surface of the moon again.
D) The turning point is at approximately $( 20,320 )$ . This is the point at which the rock reaches its maximum velocity and starts to slow down.