Answer:
Step-by-step explanation:
5000X9X9=405000x
The ball's velocity will be represented by the derivative of its distance function:

Now find the times

for which this is equal to 30, i.e. solve

This has two solutions,

, but only one is positive and falls in the interval
![[0,3]](https://tex.z-dn.net/?f=%5B0%2C3%5D)
. So the velocity reaches 30 cm/s when

.
64/3=x/1
easy, just divide
64/3=21 and 1/3 calls per hour