Joint posterior PDFs for the model Esr2-3MP based on two extended sources and image positions. We show the parameters representing the lens masses at three multiple planes. The θ_E, GH and θ_E, BGG are the Einstein radius of the group halo and the BGG at the main lens plane at z = 0.683. The x_z = 1.36 and y_z = 1.36 are the centroid of the perturber, and the θ_{E, z = 1.36} is its Einstein radius. The θ_E, S0 is the Einstein radius of S0 at z = 1.49. The three shaded areas on the joint PDFs show the 68.3%, 95.4%, and 99.7% credible regions. The 1D histograms show the marginalized PDFs for the selected mass parameters, and the vertical lines mark the 1σ confidence intervals. The θ_E, S0 shows strong degeneracies with θ_E, BGG, θ_E, GH, and θ_{E, z = 1.36}.