Univ Physicsresistance
posted by Joanna .
A hollow cylindrical resistor with inner radius r1 and outer radius r2, and length l, is made of a material whose resistivity is rho.
A.Find the resistance for current that flows radially outward. Divide the resistor into concentric cylindrical shells and integrate. Express your answer in terms of the variables r1,r2, l,rho, and appropriate constants.
B.Evaluate the resistance R for such a resistor made of carbon whose inner and outer radii are 1.0mm and 3.0mm and whose length is 4.5cm. rho=15*10^5 omega*m
C.What is the resistance in part B for current flowing parallel to the axis?

I think I got part A and B. I need help on part C. How do I do it?