A spring with spring constant k = 800 N/m is extended 12 cm from its equilibrium position. A spring with 6.0 cm extension from equilibrium will have the same potential energy as the first spring if its spring constant is
1) 200 N/m.
2) 400 N/m.
3) 800 N/m.
4) 1600 N/m.
5) 3200 N/m.
Answer: 5