A long, nonconducting, solid cylinder of radius \( 4.0 \mathrm{~cm} \) has a nonuniform volume c...

A long, nonconducting, solid cylinder of radius \( 4.0 \mathrm{~cm} \) has a nonuniform volume charge density \( \rho \) that is a function of radial distance \( r \) from the cylinder axis: \( \rho=A r^{2} \). For \( A=6.3 \mu \mathrm{C} / \mathrm{m}^{5} \), what is the magnitude of the electric field at (a) \( r=3.0 \mathrm{~cm} \) and (b) \( r=5.0 \mathrm{~cm} \) ?