You want to get from a point a on the straight shore of the beach to a buoy which is 60 meters out in the water from a point b on the shore. b is 70 meters from you down the shore. if you can swim at a speed of 3 meters per second and run at a speed of 5 meters per second, at what point along the shore, x meters from b, should you stop running and start swimming if you want to reach the buoy in the least time possible?