Minimum Area

You are provided four points $p$ on $x$-axis, $q$ on $y$-axis, $r$(min - value on $x$-axis) and $s$(min - value on $y$-axis). Initially, $p≥r$ and $q≥s$. You can perform the following operation less than or equal to n times: Select either $p$ or $q$ and reduce it by $1$. Where point $p$ cannot become less than $r$, and point $q$ cannot become less than $s$. Find the minimum possible area under