An Agricultural Sprinkler Distributes Water in a Circular Pattern of Radius

Short Answer

An agricultural sprinkler distributes water in a circular pattern of radius $100 \mathrm { ft }$ . It supplies water to a depth of $e ^ { - r }$ feet per hour at a distance of $r$ feet from the sprinkler. What is the total amount of water supplied per hour to the region inside the circle of radius 15 feet centered at the sprinkler?