In the center of a thick-walled metal shell radii R1 = 5 cm and R2 = 10 cm, the charge carrier nC q = 10, is a point charge q0 = 5 nC. Find strength and potential of the electrostatic field at the distance: 1) r1 = 3 cm 2) r2 = 7 cm 3) r3 = 15 cm from the center. Build dependency graphs quality Er (r) and f (r).