A wandering backpacker is being chased in a straight line by an angry black bear in a national park. The backpacker can sprint at a speed of 6.0 m/s, while a bear can run at a speed of 8.0 m/s. If the shelter is 50.0 m away and the bear is 18 m behind the backpacker, the difference in the time it takes for the backpacker and the bear to reach the shelter is a.b ´ 10-c s. The values of a, b, and c, respectively, are