A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. When the spring is 4.0 cm longer than its equilibrium length, the speed of the block is 0.50 m/s. What is the greatest speed of the block?
a) 0.32 m/s
b) 0.55 m/s
c) 0.71 m/s
d) 0.87 m/s
