Lens system configurations of the close (upper panel) and wide (lower panel) 2L2S solutions. Notations are same as those in Fig. 4, except that there are two lens masses and two source trajectories. The source trajectories of the first and second source stars are marked by S₁ and S₂, respectively. The empty circles on the source trajectories represent the source positions at a certain epoch, and the sizes of the circles are scaled to the caustic size.