{
  "equations": [
    "25u/2=10T+5C",
    "13u/2=5C"
  ],
  "solution": {
    "T_over_u": "3/5",
    "C_over_u": "13/10"
  },
  "source_values": {
    "u": 100,
    "T": 60,
    "C": 130
  },
  "proof": "Invert thetwoequations inT,C; determinant50 is nonzero, so conditionsare necessaryandsufficient.",
  "not_constrained": "SojournS doesnotappear",
  "source_cost": "The rowmasks do not entailthese ratios; theyare additionalobserved cross-sourcecalibration relations."
}