The diagram shows a coaxial cable with an inner conducting wire of diameter d₁  =  1.23 mm and an outer conducting sheath of inside diameter d₂  =  7.80 mm. Mylar (κ  =  3.10) fills the space between the inner wire and the outer conducting sheath. An outer plastic sheath protects the cable from damage.

How much energy is stored in 18.0 m of this cable if the inner wire carries a charge density λ  =  2.94×10^-9 C/m?