{ x8 = x3 + x5 + x2 + x6 + x1 + x4,
  1*k18*x1 + 1*k18*x2 + 1*k18*x3 + 1*k18*x4 + 1*k18*x5 + 1*k18*x6 + 1*k18*x7 = k18*k19 }