A hollow non-conducting spherical shell has inner radius R1 = 10 cm and outer radius R2 = 17 cm. A charge Q = -25 nC lies at the center of the shell. The shell carries a spherically symmetric charge density ρ = Ar for R1 < r < R2 that increases linearly with radius, where A = 16 μC/m4. Write an equation for the radial electric field in the region r < R1 in terms of Q, r, and Coulomb's constant k. You may take the positive direction as outward. Er < R1