[ Eq(1*x2 + 1*x3, k56),
  Eq(1*x4 + 1*x16, k57),
  Eq(1*x5 + 1*x15, k58),
  Eq(1*x6 + 1*x17, k59),
  Eq(1*x7 + 1*x8, k60),
  Eq(1*x10 + 1*x11, k61),
  Eq(1*x12 + 1*x13, k62),
  Eq(1*x20 + 1*x21, k63) ]