Consider an infinitely long solid cylinder with radius R_0 and volume charge density rho=rho_0*r(r≤R_0) where rho_0 is a constant. Use first principles to determine the electric field E(vector) for r

Question

Consider an infinitely long solid cylinder with radius R_0 and volume charge density rho=rho_0*r(r≤R_0) where rho_0 is a constant. Use first principles to determine the electric field E(vector) for r<R_0.