[WaterTank]
  free  A
  free  V
  free  d[:]
  fixed M
  fixed rho
  cons  A ≥ 2·(d[0]·d[1] + d[0]·d[2] + d[1]·d[2])
  cons  V = d[0]·d[1]·d[2]
  cons  M = V·rho
