Twelve soldiers had to get to a place twenty miles distant with the quickest possible dispatch, and all had to arrive at exactly the same time. They requisitioned the services of a man with a small car. "I can do twenty miles an hour," he said, "but I cannot carry more than four men at a time. At what rate can you walk?" "All of us can do a steady four miles an hour," they replied. "Very well," exclaimed the driver, "then I will go ahead with four men, drop them somewhere on the road to walk, then return and pick up four more (who will be somewhere on the road), drop them also, and return for the last four. So all you have to do is to keep walking while you are on your feet, and I will do the res t." They started at noon. What was the exact time that they all arrived together?