This question involves the concept of the law of conservation of energy.
The spring constant of the cable is "915.6 N/m".
According to the law of conservation of energy, energy can neither be created nor be destroyed. It can only change from one form to another form. In this scenario, the elastic potential energy stored by the cable will completely be transformed into the gravitational potential energy at the highest point.
[tex]Loss\ of\ Elastic\ Potential\ Energy=Gain\ in\ Gravitational\ Potential\ Energy[/tex]
[tex]\frac{1}{2}kx^2=mgh\\\\k= \frac{2mgh}{x^2}[/tex]
where,
Therefore,
[tex]k=\frac{2(160\ kg)(9.81\ m/s^2)(42\ m)}{(12\ m)^2}[/tex]
k = 915.6 N/m
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