16 4. A 0.60kg mass is placed at the end of a spring and oscillates back and forth as the spring changes length. The spring is compressed a maximum of 0.3m. The spring has a spring constant of 210.0 N/m, No friction is present. a) What is the restoring force when the spring is extended by 0.2m? b) What is the maximum elastic potential energy that is possible in this system? c) What is the maximum kinetic energy that is possible in this system