{ x8 = 134/5*(67957/25000)^((-9/50)*t),
  x50 = k225 - (x13 + x14 + k208 + k209 + x18 + x19 + k210 + k211 + x23 + x24 + k212 + k213 + x28 + x29 + k214 + k215 + x33 + x34 + k216 + k217 + x38 + x39 + k218 + x41 + x43 + x44 + k219 + x46 + x47) }