I got parts a and b but am having trouble getting part c and d. can someone please help me? thanks in advance! Figure 8-40 shows an 8.00 kg stone resting on a spring. The spring is compressed 8.0 cm by the stone. Fig. 8-40 (a) What is the spring constant? 9.8 N/cm by mg/x(compression) (b) The stone is pushed down an additional 30.0 cm and released. What is the elastic potential energy of the compressed spring just before that release? 70.8 J by convert A to N/m then convert compression to m and then use .5kx^2 to get the answer (c) What is the change in the gravitational potential energy of the stone-Earth system when the stone moves from the release point to its maximum height? J gravitational potential energy is mgy but i don't know y (d) What is that maximum height, measured from the release point? m y=(.5mv^2)/mg I know i have to use this eqn. but i don't know v.