In a noninjury chain-reaction accident on a foggy freeway, car 1 (mass of 2000 kg) moving at 15.0 m/s to the right elastically collides with car 2, initially at rest. The mass of car 2 is 1500 kg. In turn, car 2 then goes on to lock bumpers (that is, it is a completely inelastic collision) with car 3, which has a mass of 2500 kg and was also at rest. Determine the speed of all cars immediately after this unfortunate accident.