Critical curves for the lens plane at z = 1.36 in three-lens-plane models. The Esr2−3MP model uses an isothermal mass profile to model the mass distribution at z = 1.36. Meanwhile, the Esr2−3MP (MS) model uses a constant mass sheet, and the Esr2−3MP (MS + Shear) model uses a constant mass sheet with an external shear. The purple and gray arrows indicate the mass concentrations predicted by the external shear at z = 1.36 and z = 0.683, respectively, in the model Esr2−3MP (MS + Shear). The critical curves for these models nearly overlap, with the orange and blue lines largely hidden beneath the purple line.