Hey Hasti,

In this problem the motion of the ball is against the Direction of gravity. So the velocity given is initial velocity , u= 39.4 m/s.

The final velocity at the maximum height will be, v=0. And at all points the acceleration is same as the acceleration due to gravity, g=9.8 m/(s^2).

So, at the highest point of motion , v =0 and a=g=9.8 m/(s^2)

Hope this helps you.