Chapter 21 - Electric Current and Direct-Current Circuits - Problems and Conceptual Exercises - Page 755: 18

$L=141.41m$

We know that $R=\frac{\rho L}{A}$ We plug in the known values to obtain: $R=\frac{1.68\times 10^{-8}.L}{\pi (0.22\times 10^{-3})^2}$ As $V=IR$ We plug in the known values to obtain: $15=0.96\times\frac{1.68\times 10^{-8}.L}{\pi (0.22\times 10^{-3})^2}$ This simplifies to: $L=141.41m$