Energy Density: an Ideal Air-Filled Parallel-Plate Capacitor Has Round Plates

Multiple Choice

Energy density: 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 density between the plates was u₀, what is the new energy density?

A) 16u₀
B) 4u₀
C) u₀
D) u₀/4
E) u₀/16