The answer is
3^66483360316461674016
A circle is a collection of points all of which are on the circumference of the circle. If you use algebra and (x-h)^2 + (y-k)^2 = r^2 and the info contained in the coordinates (x,y) of each city, you can find h, k and r. Then r is the (equal) distance between each city and the center of the circle, where the new tower will be built.
The answer is a............
