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9. [12] A spherical cavity of radius 8.00 cm is centered at the center of a metal sphere of radius 16.00 cm. A point charge of 6.00 uC rests at the center of the cavity. The metallic spherical shell carries a net charge of -16.0 MC. (a) [4] What is the surface charge (with proper sign) on the inner surface of the metallic spherical shell? (b) [4] What is the surface charge (with proper sign) on the outer surface of the metallic spherical shell? (c) [4] What is the electric field strength at a point just outside the outer surface of the metal spherical shell