A circular swimming pool has a radius of 20 feet. A fence is going to be built so that there is a 4-foot space around the entire pool. What is the length of the fence? Sunitha solved the problem as shown.

A circle with radius 20 feet. A larger circle is 4 feet larger than the smaller circle. Radius = 24 feet. Circumference = 24 pi.

What was her error?