A BMW of mass 2.26 × 103 kg is traveling at 41.5 m/s. It approaches a 1.40 × 103 kg Volkswagen going 23.9 m/s in the same direction and strikes it in the rear. Neither driver applies the brakes. Neglect the relatively small frictional forces on the cars due to the road and due to air resistance. If the collision slows the BMW down to 34.0 m/s, what is the speed of the VW after the collision? I've tried to solve this question by finding the final velocity of the Volkswagen (VW) using this formula vwf = (mb(vb-vbf)+mwvw) / mb and still got the incorrect answer. Please help.

A BMW of mass 2.26 × 103 kg is traveling at 41.5 m/s. It approaches a 1.40 × 103 kg Volkswagen going 23.9 m/s in the same direction and strikes it in the rear. Neither driver applies the brakes. Neglect the relatively small frictional forces on the cars due to the road and due to air resistance. If the collision slows the BMW down to 34.0 m/s, what is the speed of the VW after the collision? I've tried to solve this question by finding the final velocity of the Volkswagen (VW) using this formula vwf = (mb(vb-vbf)+mwvw) / mb and still got the incorrect answer. Please help.