{ x3 = k6*k22^k10/((k20*k8)^k10 + k22^k10),
  x4 = k7*k23^k11/((k20*k9)^k11 + k23^k11),
  x5 = k12*k22^k16/((k21*k14)^k16 + k22^k16),
  x6 = k13*k23^k17/((k21*k15)^k17 + k23^k17) }