A person standing on the roof of a building throws a ball vertically upward at an instant  $t=0$.  The ball leaves his hand with an upward speed 20m/s and it is then in free fall.  The ball rises to a certain height and then moves down. On its way down, the ball just misses to hit the roof of the building and keeps falling towards the earth. The ball hits earth at  $t=5\sec$. Considering that (i) The vertically upward direction is the positive Y-direction  (ii) The position of ball at  $t=0$ is the origin (iii) The ball does not rebound and comes to rest at the same place where it hits earth and (iv) Air resistance is negligible, answer these questions.
(Take $g=10m/s^2$)