Solve the problems below that pertain to constructing a fence. $($Let $\backslash ($ x $\backslash )$ be the length of the sides perpendicular to the river, and $\backslash ($ y $\backslash )$ the length of the parallel side.$)\backslash [\backslash$begin$\{$array$\}\{$l$\}$ x$=\backslash$square $\backslash \backslash$ y$=\backslash$square $\backslash$end$\{$array$\}\backslash ]($b$)$ How does the answer from part $($a$)$ change if the fence is divided into three equal sections by two additional lengths of fence parallel to the river. $\backslash [\backslash$begin$\{$array$\}\{$l$\}$ x$=\backslash \backslash$ y$=\backslash \backslash \backslash$hline $\backslash$end$\{$array$\}\backslash ]\backslash [\backslash$mathrm$\{$ft$\}^\{2\}\backslash ]$ maximum or minimum at each critical point of the function describing length of fence?