The best-fit lensing model for the dust continuum. Top left: the observed dirty image. Top right: the best-fit model dirty image. Bottom left: the residual map. Bottom right: the source-plane emission. The red lines mark the caustics of the lensing potential, which exhibits a naked-cusp structure. The source plane emission shows a compact bright core and a fainter outskirt with some irregular features. The total flux is 3.36  ±  0.02 mJy, and the flux magnification is 4.63  ±  0.03. The source-plane spatial resolution is ﹩0\mathop{.}\limits{^{\prime\prime} }019﹩ (about 104 pc).