A car leaves from location A at 9:00 p.m. at 90 km/h. At 9:30 p.m., an almost identical car comes towards it from place B, which is 20 km away from place A, at a speed of 70 km/h. It is dark and the road is not visible. At the other end of the town another car starts at 60 km/h. There is a driver and two passengers in the car. Snow has fallen. Exactly 500 metres away, another similar car is standing in the light of a street lamp. They all meet at time t.