Two Flat Conductors Are Placed with Their Inner Faces Separated

Two flat conductors are placed with their inner faces separated by 6.0 mm. If the surface charge density on one of the inner faces is 40 pC/m², what is the magnitude of the electric potential differences between the two conductors?

A) 36 mV
B) 18 mV
C) 32 mV
D) 27 mV
E) 14 mV