Flux and nonconducting shells. A charged particle is suspended at the center of two concentric spherical shells that are very thin and made of nonconducting material. Figure (a) shows a cross section. Figure (b) gives the net ux (Dthrough a Gaussian sphere centered on the particle, as a function of the radius r of the sphere. The scale of the vertical axis is set by $5 = 4.0 x 105 N-mZ/C. (a) What is the charge of the central particle? What are the net charges of (b) shell A and (c) shell B? (a) (b)