Maximize	$\displaystyle {f}={4}{x}+{5}{y}$
Subject to	$\displaystyle {\left.\begin{array}{ccc} {x}+{4}{y}&\le&{24}\\{x}+{5}{y}&\le&{25}\\{y}&\le&{4}\\{x}&\ge&{0}\\{y}&\ge&{0}\end{array}\right.}$

Maximum is at (If needed, separate points with a comma.)