Q A rollercoaster of mass 400 kg is stationary at the highest point on the track. It then drops to the lowest point through a vertical distance of 24 m.

Question

Q A rollercoaster of mass 400 kg is stationary at the highest point on the track. It then drops to the lowest point through a vertical distance of 24 m. 
Calculate: 
a) the potential energy of the car at the top of the ride. 
b) the speed of the car at its lowest point, ignoring air resistance.

My answer for (a) is 94176 N, and for (b) is 21.7 m/s

Appreciate if someone could check these answers if correct. If wrong, can they point me in the right direction. 
TIA

You used g=9.81 m/s^2, which is fine. Both of your answers are correct.

Thanks for taking the time.