min 12x1 + 12x2 + 14x3 + 14x4 + 16y2 + 18y3 + 3w1 + 3w2 + 3w3
st
  x1 - w1 = 400
  x2 + y2 + w1 - w2 = 750
  x3 + y3 + w2 - w3 = 950
  x4 + w3 = 900
  x1 < 800
  x2 < 800
  x3 < 800
  x4 < 800
  y2 < 200
  y3 < 200
  w1 < 50
  w2 < 50
  w3 < 50
end
leave