Finding ratio of the spring constant to the helicopter's mass, answer given but explanation needed!?

A helicopter descends vertically to land with a speed of 4.0 m/s. If the shock absorbers have an initial length of 0.50 m, they compress to 79% of their original length and the air in the tires absorbs 21% of the initial energy as heat, what is the ratio of the spring constant to the helicopter's mass? Assume one landing gear in the craft. The answer given is 1.1 kN/kg‐m, but I don't get how to obtain this answer. Any help appreciated on this one!