477 (This is a well-known problem, versions of which are often found in books of science "puzzlers." It is sometimes called Isidro's Train Problem.) Trains A and B approach each other. Each train moves at B constant velocity 50 miles/hr relative to the earth. A bird flies back and forth from A to B, reversing instantly at each train, and flying at constant speed relative to the earth. At time t = 0, the bird leaves A, and A and B are 100 miles apart. The time required for the bird to make its first round trip is 0.5 hours. (Continued on next page)477 (continued) (a) Find the velocity of the bird relative to the earth. ( b ) Find the total distance flown by the bird before the trains meet. (A harder question that you might want to think about is finding the number of round trips made by the bird before the trains meet.)