A coaxial cable carries a current \(I_{\text {wire }}\) in its inner conducting wire and a current \(I_{\text {shell }}\) in its outer conducting shell. The radius of the wire is \(R_{\text {wire }}\), the distance from the cable center to the inside of the shell is \(R_{\text {shell, }}\), and the distance from the center to the outer edge of the shell is \(2 R_{\text {shell. }}\). Determine all locations (if any exist) at which the magnetic field magnitude is zero if \(

(a) I_{\text {wire }}=I_{\text {shell }}\),

(b) \(I_{\text {wire }}=-I_{\text {shell }}\), and

(c) \(I_{\text {wire }}=-I_{\text {shell }} / 2\).