Problem: A horizontal spring, resting on a frictionless tabletop, is stretched 12cm from its unscratched configuration and a 1.00-kg mass is attached to it. The system is released from rest. A fraction of a second later, the spring finds itself compressed 2.8cm from its unscratched configuration.
Part A: How does its final potential energy compare to its initial potential energy? (Give your answer as a ratio, final to initial.)
Please explain and show work so I can do it next time!