A solid insulating sphere of radius \(R\) contains a non-uniform volume charge density \(\rho_1(r) = \rho_0 \left(\dfrac{r}{R}\right)\), where \(\rho_0\) is a positive constant and \(r\) is the radial distance from the center. Concentric with this sphere is a thick insulating spherical shell with inner radius \(2R\) and outer radius \(3R\). The thick shell contains a non-uniform volume charge density \(\rho_2(r) = -\rho_0 \left(\dfrac{R}{r}\right)\). Which of the following expressions correctly gives the magnitude of the electric field \(E(r)\) in the region \(2R < r < 3R\) as a function of \(r\)?