A long, straight wire has fixed negative charge with a linear charge density of magnitude $3.6 \mathrm{nC} / \mathrm{m}$. The wire is to be enclosed by a coaxial, thin-walled nonconducting cylindrical shell of radius $1.5 \mathrm{~cm}$. The shell is to have positive charge on its outside surface with a surface charge density $\sigma$ that makes the net external electric field zero. Calculate $\sigma$.

$3.8 \times 10^{-8} \mathrm{C} / \mathrm{m}^2$