As a high-speed passenger train, traveling at 88.0 km/h, rounds a bend, the engineer realizes that a locomotive has improperly entered the train's track from a sidetrack distance d= 420 m ahead. That locomotive is moving at 22.0 km/h. The engineer immediately applies the brakes to reduce train's speed to the speed of the locomotive ahead. What minimal magnitude of the resulting constant acceleration is needed to prevent a collision? I thought the equation to use would be Vfinal^2=Vinitial^2+2a(Xfinal-Xinitial). I converted the numbers so the answer would be in m/s^2 but that didn't work and then I tried leaving the numbers so my answer would be in km/h^2 but that didn't work either. Any help?