When a high-speed passenger train traveling at vP = 160 km/h rounds a bend, the engineer is shocked to see that a locomotive has improperly entered onto the track from a siding and is a distance D = 652 m ahead (see the figure). The locomotive is moving at vL = 30 km/h. The engineer of the passenger train immediately applies the brakes. Assume that an x axis extends in the direction of motion. What must be the constant acceleration along that axis if a collision is to be just avoided?