A 1200 kg car carrying four 82 kg people travels over a rough "washboard" dirt road with corrugations 4.0 m apart which causes the car to bounce on...

A 1200 kg car carrying four 82 kg people travels over a rough "washboard" dirt road with corrugations 4.0 m apart which causes the car to bounce on its spring suspension. The car bounces with maximum amplitude when its speed is 18 km/h. The car now stops, and the four people get out. By how much does the car body rise on its suspension owing to this decrease in weight? can you show the equations for this because that is what im having difficulty deriving