{ 1*k21*x1 + 1*k21*x2 + 1*k21*x3 + 1*k21*x4 = k21*k25,
  1*k21*x5 + 1*k21*x6 + 2*k21*x8 + 1*k21*x9 + 1*k22*x12 + 2*k22*x13 + 1*k22*x14 + 1*k22*x15 = k21*k26 + k22*k27,
  1*k21*x7 + 1*k21*x9 + 1*k22*x15 + 1*k22*x16 = k21*k28 + k22*k29 }