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Use one compatible pricing record
In the original 100→130/80 model at 5% for the period, call value is 14.285714 and put value 9.52381. The period discount factor is 1/1.05. Both payoffs are European and no underlying income is supplied.
Subtract the claim prices
The difference is 4.761905. Current underlying minus strike present value is 100−100/1.05=4.761905. The two expressions agree.
Inspect the terminal reason
Call payoff minus put payoff is S−100 in either state. The matching underlying-minus-terminal-strike portfolio has the same terminal expression, motivating the compatible current-cost identity.
| State | Call | Put | Call minus put |
|---|---|---|---|
| 130 | 30 | 0 | 30 |
| 80 | 0 | 20 | −20 |
Do not change conventions between identities
Different expiry, exercise rights, income or funding assumptions require their own treatment. The agreement here checks one supplied model; it does not certify a real market quote or resolve all contract features.