Suppose we have a block mounted on a spring and define the zero point for the elastic potential energy of the system to be the relaxed position (meaning the block is positioned such that the spring is neither compressed nor stretched). What is the appropriate sign of the elastic potential energy when the block is repositioned so that the spring is \((a)\) stretched and \((b)\) compressed? (Think about what happens to the elastic potential energy when the stretched or compressed spring is released.)