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State the two compatible packages
Package A contains one underlying unit and one strike-100 put. Package B contains one strike-100 call and a certain cash amount 100 due at the same expiry. The table concerns terminal amounts, not present purchase costs.
Calculate each package
Below 100, A adds S and 100−S while B has zero call payoff plus 100. Above 100, A is S while B adds S−100 and 100. They match at every nonnegative terminal price.
Inspect the original scenarios
| Terminal price | Stock plus put | Call plus terminal cash |
|---|---|---|
| 0 | 100 | 100 |
| 80 | 100 | 100 |
| 100 | 100 | 100 |
| 120 | 120 | 120 |
| 150 | 150 | 150 |
Discount the cash only when changing dates
To compare present costs under the selected European/no-income assumptions, the terminal cash amount becomes 100D today. Using undiscounted 100 as its present cost mixes dates unless D=1. The payoff identity itself needs no such discount calculation.