The Electric Field Just Outside the Surface of a Hollow

Multiple Choice

The electric field just outside the surface of a hollow conducting sphere of radius 20 cm has a magnitude of 500 N/C and is directed outward. An unknown charge Q is introduced into the center of the sphere and it is noted that the electric field is still directed outward but has decreased to 100 N/C. What is the magnitude of the charge Q?

A) 1.5 nC
B) 1.8 nC
C) 1.3 nC
D) 1.1 nC
E) 2.7 nC