1. The problem statement, all variables and given/known data A long coaxial cable consists of an inner solid cylinder, radius a, and an outer thin coaxial cylindrical shell, radius b. The outer shell carries a uniform surface charge density σ. Find the uniform volume charge density ρ that the inner cylinder must have in order that the whole cable (inner + outer) is neutral. 2. Relevant equations Acylinder = 2πbl Vcylinder = πa2l ρ = Q/V ∇∙E = ρ/ϵ0 Qenc = ∫Vρdτ 3. The attempt at a solution I feel like I have all the relevant equations, yet, I still do not know how to start this. Any hints? Very much appreciated.