This question is about kinetic and gravitational potential energy. Look at the graph. It shows how the speed of a roller coaster car changes with the distance travelled along part of the track. The roller coaster car starts from rest at the top of the track at A. The car and its passengers have a total mass of 400 kg.

Describe how the kinetic energy and the gravitational potential energy of the car change in sections AB and BC of the journey, and calculate the difference in height of the roller coaster between A and B assuming no energy is lost. The acceleration due to gravity is 10 m/s2.