The circumcenter of a triangle is the point where the perpendicular bisectors of the sides intersect. It is also the center of the circumcircle, the circle that passes through all three vertices of the triangle
The distance of the circumcenter to the vertices of the triangle is equal to the radius of the circle
see the attached figure to better understand the problem
therefore
the answer is
The cell phone company must be place the new cell tower in the circumcenter of the triangle formed by the center of the three towns
