The Effective Area of Each Plate of a Parallel Plate $\kappa$

The effective area of each plate of a parallel plate capacitor is 2.1 m². The capacitor is filled with neoprene rubber ( $\kappa$ = 6.4) . When a 6.0-V potential difference exists across the plates of the capacitor, the capacitor stores 4.0 µC of charge. Determine the plate separation of the capacitor.

A) 7.2 × 10^-5 m
B) 3.0 × 10^-4 m
C) 1.8 × 10^-4 m
D) 5.3 × 10^-4 m
E) 8.2 × 10^-5 m