[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
