A 4-kg projectile is fired vertically with an initial velocity of 90 m/s, reaches a maximum height and falls to the ground. The aerodynamic drag D has a magnitude D = 0.0024 v2 where D and v are expressed in newtons and m/s, respectively. Knowing that the direction of the drag is always opposite to the direction of the velocity, determine

(a) The maximum height of the trajectory,

(b) The speed of the projectile when it reaches the ground.