A coaxial-cable with an inner diameter of 1 mm and outer diameter of 2.4 mm is filled with a dielectric of relative permittivity 10.89. Given $${\mu _0} = 4\pi \times {10^{ - 7}}{\text{H/m}},\,{\varepsilon _0} = \frac{{{{10}^{ - 9}}}}{{36\pi }}{\text{F/m}}{\text{.}}$$
The characteristic impedance of the cable is