A point charge q1 = +7e is fixed at the origin of a rectangular coordinate system, and a point charge q2 = -10e is fixed at x = 7.1 nm, y = 0. The locus of all points in the xy plane for which V = 0 (other than infinity) is a circle centered on the x axis. Find (in nm) (a) the location xc of the center of the circle and (b) the radius R of the circle. (c) Is the xy cross section of the 5 V equipotential surface also a circle? 1 = yes, 2 = no. Give the number of the correct answer.