Hey,
I'm new, so sorry if I somehow messed up by posting in the wrong place. Anyway, onto my question: I defined two functions
 
\[Beta][w_, x_] := 
 Piecewise[{{0, 
    w < 150 && x < 150}, {1/
     3, (w < 150 && 150 <= x < 300) || (150 <= w < 300 && 
       x < 150)}, {1/
     2, (w < 150 && x >= 300) || (x < 150 && w >= 300)}, {2/
     3, (150 <= w < 300 && 150 <= x < 300)}, {5/
     6, (150 <= w < 300 && x >= 300 ) || (150 <= x < 300 && 
       w >= 300 )}, {1, w >= 300 && x >= 300}}]
and 
 
\[Gamma][w_, x_, y_] := 
 Piecewise[{{0, 
    w < 150 && x < 150 && y < 150}, {1/
     3, (150 <= w < 300 && x < 150 && y < 150) || (150 <= x < 300 && 
       w < 150 && y < 150) || (150 <= y < 300 && w < 150 && 
       x < 150)}, {1/
     2, (w >= 300 && x < 150 && y < 150 ) || (x >= 300 && w < 150 && 
       y < 150 ) || (y >= 300 && x < 150 && w < 150 )}, {2/
     3, (150 <= w < 300 && 150 <= x < 300 && 
       y < 150) || (150 <= w < 300 && 150 <= y < 300 && 
       x < 150) || (150 <= y < 300 && 150 <= x < 300 && w < 150)}, {5/
     6, (w >= 300 && 150 <= x < 300 && y < 150) || (w >= 300 && 
       150 <= y < 300 && x < 150) || (x >= 300 && 150 <= w < 300 && 
       y < 150) || (x >= 300 && 150 <= y < 300 && 
       w < 150) || (y >= 300 && 150 <= w < 300 && 
       x < 150) || (y >= 300 && 150 <= x < 300 && 
       w < 150)}, {1, (w >= 150 && x >= 150 && y >= 150) || (w < 150 && 
       x >= 300 && y >= 300) || (x < 150 && w >= 300 && 
       y >= 300) || (y < 150 && x >= 300 && w >= 300)}}]
and then use them along with a third piecewise function in one variable 
 
\[Alpha][w_] := 
 Piecewise[{{0, w < 150}, {1/3, 150 <= w < 300}, {1/2, w >= 300}}]
The piecewise functions themselves all work, but I get an error when evaluating: 
 
NMinimize[{w + x + y + z, 
  w + \[Alpha][w] x + \[Beta][w, x] y + \[Gamma][w, x, y] z >= 1/3 && 
   w \[Element] PositiveIntegers && x \[Element] PositiveIntegers && 
   y \[Element] PositiveIntegers && 
   z \[Element] PositiveIntegers }, {w, x, y, z}]
Can anyone tell me why this doesn't work and if there is some way to do this correctly? Thank you very much!