A charged particle is held at the center of two concentric conducting spherical shells. Figure (a) shows a cross section. Figure (b) gives the net flux o through 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 0, = 4.5 x 105 N-m2/c. What are (a) the charge of the central particle and the net charges of (b) shell A and (c) shell B? B -20, (a) (b) O (10 N. m2/C)