A Runaway Railroad Car,with Mass 30 × 10⁴ Kg,coasts Across

A runaway railroad car,with mass 30 × 10⁴ kg,coasts across a level track at 2.0 m/s when it collides with a spring-loaded bumper at the end of the track.If the spring constant of the bumper is 4.0 × 10⁶ N/m,what is the maximum compression of the spring during the collision? (Assume the collision is elastic. )

A) 0.77 m
B) 0.55 m
C) 0.34 m
D) 1.07 m