Calculating Resistance of a Disk | Homework Problem Solution

[Gyroscope]

Homework Statement

A disk with width b and radius a.
An element of resistance is:

$$dR=\rho \frac{2\pi r}{bdr}$$

How do I integrate this?

Thanks in advance.

Homework Equations

The Attempt at a Solution

 

[berkeman]

I don't understand your volume element. You are trying to get the total resistance between what two places? A point on one edge of the disk to a point on the other side, or from the center out to the perimiter, or what?

 

[Gyroscope]

It's the sum of the resistances of each ring of the disk.