4. A stone nudged off the Royal Gorge Bridge near Cañon City, Colorado, falls 1053 feet before hitting water. Because its speed increases as it falls, the distance it travels each second increases. During the
first second, it drops 16 feet. During the next second, it drops an additional 48 feet. During the third
second, it drops another 80 feet. The distances traveled each second form an arithmetic sequence:
16, 48, 80, ...
5th recond? Find and use the explicit formula.