Senior Kangaroo 2022 Q4

The rectangles $S^1$ and $S^2$ are drawn on a set of coordinate axes. $S^1$ has vertices at $(0, y)$; $(x, y)$; $(x, 4)$; and $(0, 4)$, where $x < 9$ and $y < 4$. $S^2$ has vertices at $(x, 0)$; $(9, 0)$; $(9, y)$; and $(x, y)$. The rectangles are equal in area. What is the value of $360xy$?