Critical curves (black) and caustics (grey) of the lens models. Dashed (solid) curves correspond to the most probable lens model with image positions (extended image surface brightness) as constraints. The dot-dashed curve in the inset marks the cut of the satellite. The cross (plus) symbol denotes the modelled centroid position of the primary (satellite) lens. The three types of open symbols mark the three sets of multiple image systems. The solid symbols are the corresponding modelled source positions based on the most probable lens parameters from the extended image modelling. The shapes of the critical and caustic curves are similar for the two models, but the model based on image positions (dashed) has a rounder primary lens with higher external shear.