A 39.0-m length of coaxial cable has an inner conductor that has a diameter of 2.58 mm and carries a charge of 8.10 µC. The surrounding conductor has an inner diameter of 7.27 mm and a charge of -8.10 µC. Assume the region between the conductors is air.
(a) What is the capacitance of this cable?
(b) What is the potential difference between the two conductors?