Answer:
a)
,
, b)
, c)
, d)
, e)

Step-by-step explanation:
a) The velocity function is determined by deriving the position function in time:

Velocities after 2 seconds and 4 seconds are, respectively:


b) The maximum height is reached when velocity is equal to zero:

The time when the projectile reaches the maximum height:

c) The maximum height is:


d) The projectile hits the ground when height is equal to zero:

The roots of the second order polynomial are presented below:


The first one is the only reasonable solution in physical terms.

e) The velocity of the projectile when it hits the ground is:

