6. [-/1 Points] DETAILS SCALCET9 6.4.012. If 5.4 J of work is needed to stretch a spring from 17 cm to 23 cm and another 9 J is needed to stretch it from 23 cm to 29 cm, what is the natural length (in cm) of the spring? cm Need Help? Read It 7. [-/1 Points] DETAILS SCALCET9 6.XP.4.004. Find the work W done (in ft-lb) if a constant force of 80 lb is used to pull a cart a distance of 190 ft. W = ft - lb Need Help? Read It