An electric-dipole antenna, broadcasting microwave electromagnetic radiation for mobile communications, is located on the roof of a 113-m-high building and is oriented vertically. Two observers measure the signal strength (radiation intensity) from this antenna. Observer A is on the roof of another building, at the same height as the antenna and at a distance of 1.77 km from it. Observer B is on the street, with a direct-line distance of only 169 m from the antenna. What is the ratio of the signal strength measured by B, IB, to that measured by A, IA?