Oscillatory motion and Hooke's law

[tarzanna]

Homework Statement

Four people, each with mass of 71.3 kg, are in a car with a mass of 1130 kg. An earthquake strikes. The vertical oscillations of the ground surface make the car bounce up and down on its suspension springs, but the driver manages to pull off the road and stop. When the frequency of the shaking is 1.40 Hz, the car exhibits a maximum amplitude of vibration. The earthquake ends and the four people leave the car as fast as they can. By what distance does the car's undamaged suspension lift the car's body as the people get out?

Homework Equations

k=m(2pi*f)^2
x=F/-k
F=ma

The Attempt at a Solution

m=4*71.3 kg + 1130kg = 1415.2kg

1415.2kg (2pi*1.4)^2 = 109505 = k

x=(1415.2kg*9.8m/s^2) / 109505 = 0.127 m

This was not the correct answer. Where am I going wrong? Thank you.

 

[vector3]

Spring constant K look good... however, only 4 people get out of the car and we're removing the weight of the car and the people?