Whitch family has full valence energy level

Astone weighing 1.5 kilograms is resting on a rock at a height of 20 meters above the ground. the stone rolls down 10 meters and comes to rest on a patch of moss. the gravitational potential energy of the stone on the moss is joules.

If anyone who can me with this hw? i would really appreciate it

An object dropped from cliff falls with a constant acceleration of 10 metre per second square find its speed of two seconds after it was dropped