B.
This equation represent the position of the ball if we derivate we find the speed
we replace the speed by 0 to solve t, the value of t will be seconds when the heigth is maximum
After 2 seconds the heigth is maximum
C.
We replace a heigth 0 on the first equation to find when the ball hit the ground
it is a polynomial then we can use quatratic formula to solve
where -8 is a, 35 is b and 6 c
replacing
simplify
we obtan to values for t
we chose the second value because the time cant be negative
then time when the ball hit the ground is 4.54 seconds