A Conducting Sphere Carries a Net Charge of +6 µC

A conducting sphere carries a net charge of +6 µC.The sphere is located at the center of a conducting spherical shell that carries a net charge of -2 µC.Determine the excess charge on the outer surface of the spherical shell.

A) -4 µC
B) +4 µC
C) -8 µC
D) +8 µC
E) +6 µC