Lens system configurations according to the wide (upper panel) and close (lower panel) 3L1S solutions. In each panel, the nested concave curve represents the caustic, the line with an arrow is the source trajectory, and the three filled red dots marked by M₁, M₂, and M₃ indicate the positions of the lens components. The caustic curve and the source trajectory according to the static 2L1S model are drawn in gray to show the caustic variation by the third body M₃. Other notations are same as those in Fig. 3.