Chapter 27, Problem 66EAP

A $0.\text{6}0$ -mm-diameter wire made from an alloy (a combination of different metals) has a conductivity that decreases linearly with distance from the center of the wire: $\sigma \left(r\right)={\sigma }_0-cr$ , with ${\sigma }_0=5.0\times {10}^7{\Omega }^{-1}{\text{m}}^{-1}$ and $c=1.2\times {10}^{11}{\Omega }^{-1}{\text{m}}^{\text{-2}}$ . What is the resistance of a $\text{4}.0$ m length of this wire?