Energy Density: How Much Energy Is Stored in a Room

Multiple Choice

Energy density: How much energy is stored in a room 3.0 m by 4.0 m by 2.4 m due to the earth's magnetic field with a strength of 5.0 × 10^-5 T? (μ₀ = 4π × 10^-7 T ∙ m/A)

A) 570 mJ.
B) 29 mJ.
C) 10 mJ.
D) 100 mJ.
E) 57 mJ.