An Ideal Air-Filled Parallel-Plate Capacitor Has Round Plates and Carries

Multiple Choice

An ideal air-filled parallel-plate capacitor has round plates and carries a fixed amount of equal but opposite charge on its plates. All the geometric parameters of the capacitor (plate diameter and plate separation) are now DOUBLED. If the original energy stored in the capacitor was U₀, how much energy does it now store?

A) 4U₀
B) 2U₀
C) U₀
D) U₀/2
E) U₀/4