A thin metal cylinder of length L and radius R is coaxial with a thin metal cylindrical shell of length L and larger radius Rs. The space between the cylinders is filled with a material with resistivity p. A battery is connected to the two conducting pieces such that there is a potential difference AV between them which causes a current I to flow radially from the inner cylinder to the outer one. Find an expression for the resistance R of this device. (Remember that the expression R=PL/ A was derived under specific assumptions and doesn't apply here)