Summary of the SIE+shear mass model with two sources. The flux of the measured images (red), and predicted images (black), are proportional to the circle areas; these circles are centred on the relevant positions, along with red crosses showing the positions and astrometric uncertainties of the measurements. Critical curves and caustics are shown in green and blue, respectively. The two quasars are marked with red crosses, with Q1 corresponding to images ABCD, and Q2 to EF.