Materials and solids

How should I work out this question?

Q)
Energy stored per unit mass (Jkg^-1)

Modem spring steel - 130
Tendon in leg - 2500
Rubber cord. - 8000

Show that a car of mass 1200kg would need steel springs of total mass approximately equal to 3kg to store energy when it encounters pot-holes of depth 3 cm
(3 marks)

I appreciate all solutions and suggestions a lot!

Hi there, so you need to think about the change in potential energy when the car drops 3 cm
So as you know the potential energy change will be $E=mgh = 1200\times 10 \times 0.03 = 360 J$
Thus the spring needs to absorb 360 J worth of energy.
This is equivalent to 360/130= 2.76 kg which is about 3, I guess