Lens system configurations. Two upper panels show the configurations of the inner and outer 2L1S solutions with u₀ > 0 and the bottom panel shows the configuration of the 1L2S solution with u_0,1 < 0. In each of the panels showing the 2L1S configurations, the red cuspy figures represent caustics, the line with an arrow is the source trajectory, and grey curves encompassing the caustic are equi-magnification contours. In the panel of the 1L2S solution, the black filled dot represent the lens, and the blue and red curves denote the trajectories of the primary (marked by S₁) and secondary (marked by S₁) source stars, respectively.