A 1000 kg roller coaster is at the top of a 20 m hill initially moving at 5 m/s. It goes down the hill to ground level, then up a hill that is 10 m high, and then back down to 5 m above ground level. There is no friction between the roller coaster and the track. Calculate:

a) Initial Mechanical Energy of the Roller Coaster

b) the velocity of the roller coaster at the bottom of the 20 m hill (ground level)