Answer
$5.24\times 10^{-4}m$
Work Step by Step
We know that
$R=\frac{\rho L}{A}$
$R=\frac{\rho L}{\frac{\pi d^2}{4}}$
We plug in the known values to obtain:
$0.07=\frac{5.67\times 10^{-8}(0.27)}{\frac{\pi d^2}{4}}$
$0.07=\frac{1.926\times 10^{-8}}{d^2}$
$\implies d^2=\frac{1.926\times 10^{-8}}{0.07}$
$\implies d^2= 27.5\times 10^{-8}$
$\implies d=5.24\times 10^{-4}m$