CylinderCalcHeightFromRadius[r_, volume_] := N[volume/(\[Pi]*r^2)];

CylinderVolume[r_, v_] := N[\[Pi]*r^2*v];

CylinderArea[r_, v_] := N[2*\[Pi]*r*(r + v)];

RectanglePerimeter[a_, b_] := 2*(a + b);

opt1[x_] := Module[{total = 30},
   If[x[[1]] + x[[2]] > total,
     Return[0],
     Return[-x[[1]]*x[[2]]]
     ];
   ];

opt2[x_] := Module[{perimeter = 20, a = x[[1]], b = x[[2]]},
   If[RectanglePerimeter[a, b] > perimeter,
     Return[0],
     Return[-a*b]
     ];
   ];

opt3[x_] := Module[{volume = 27, r = x[[1]]},
   Return[\[Pi]*r^2 + 2*volume/r];
   ];