A positive point charge (q = +6.6 x 10-8 C) is surrounded by an equipotential surface A, which has a radius of rA = 2.7 m. A positive test charge (q0 = +4.6 x 10-11 C) moves from surface A to another equipotential surface B, which has a radius rB. The work done by the electric force as the test charge moves from surface A to surface B is WAB = -8.2 x 10-9 J. Find rB.