Aspherical, non-conducting shell of inner radius r1 = 10 cm and outer radius r2 = 15 cm carries a total charge q = 15 μc distributed uniformly throughout the volume of the shell. what is the magnitude of the electric field at a distance r = 12 cm from the center of the shell? (k = 1/4πε0 = 8.99 × 109 n ∙ m^2/c^2)