Two train stations are 50 miles apart. At noon, a train starts out from each station heading for each other. Just as they pull out, a hawk flies into the air in front of the first train and flies ahead to the front of the second train. When the hawk reaches the second train, it turns around and flies toward the first train. The hawk continues this way until the trains meet. Assume that both trains travel at 25 mph and the hawk flies at a constant speed of 100 mph. How many miles will the hawk have flown when the trains meet?