Pooters and dooters are 1/3 of the way across a one mile railway bridge when they notice that a train is coming towards the bridge. sadly, the bridge is only wide enough for the train. thinking quickly they determine that if they run back to the side of the bridge where the train is approaching (1/3 of the bridge length) they will get there just as the train arrives. they further determine that if they keep running to the other end of the bridge, they will also get there just as the train arrives. if they can run 12 mph, how fast is the train travelling and how far away is it when they need to start running?