An air-filled capacitor is formed from two long conducting cylindrical shells that are coaxial and have radii of and The electric potential of the inner conductor with respect to the outer conductor is ( k = 1/4 πε 0 = 8.99 × 10 9 N • m 2/C 2) The maximum energy density of the capacitor is closest to:

a.1.7 10-4 J/m3.
b.2.7 10-3 J/m3.
c.6.7 10-4 J/m3.
d.1.3 10-3 J/m3.
e.3.4 10-3 J/m3.