A spherical conductor with radius 2.00 cm is centered on the origin and holds charge q1=-250 nC. It is surrounded by a concentric spherical conducting shell with net charge q2=+100nC. The conducting shell has inner radius 8.00 cm and outer radius 10.0 cm. The changes are in electrostatic equilibrium.
a) Find the electric flux through a spherical Gaussian surface with radius 15.0 cm, centered on the origin.
b) Find the surface charge density a(charge per area) on the outside surface of the outer spherical shell.