The inner conductor of a coaxial cable has a radius of $0.800 \mathrm{mm},$ and the outer conductor's inside radius is $3.00 \mathrm{mm} .$ The space between the conductors is filled with polyethylene, which has a diclectric constant of 2.30 and a dielectric strength of $18.0 \times 10^{6} \mathrm{V} / \mathrm{m} .$ What is the maximum potential difference that this cable can withstand?