(Geoffrey - 64) As soon as the news of bank robbery came in, a police car was sent to High Street bridge. The robbers had made their escape in a car, and the bridge was the only point of escape north of town. The police car took strategic position at point A on the map. Three patrols were assigned to patrol A-B, A-D and A-C, each going back and forth the blocks 200mx100m in size, at uniform speed of 10km/hr. All of them started from point A at 4am. On the first occasion thereafter when the three met at the car together, a radio message advised them that the robbers had escaped from south side of town. What time did the message arrive?