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Replicate a call with underlying and borrowing

A strike-100 call in the 100→130/80 model uses 0.6 underlying units and current borrowing 45.714286.

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Calculate both holder payoffs

The hypothetical call pays max(130−100,0)=30 in the higher state and max(80−100,0)=0 in the lower. The factor from today to that expiry is 1.05. No paid option premium is used as an input to this valuation.

Solve the replicating holdings

Subtracting the two terminal equations gives Δ=(30−0)/(130−80)=0.6. To make the lower state zero, terminal cash must be −0.6×80=−48. Its current value is −48/1.05=−45.714286.

Check the complete terminal portfolio

Call state check
StateUnderlying holding valueCash repaymentMatched call amount
Higher0.6×130 = 78−4830
Lower0.6×80 = 48−480

Add the time-zero costs

The underlying holding costs 60 today. Subtract current borrowing 45.714286 to obtain model value 14.285714. The match uses fractional units and common-rate financing assumptions; real costs or funding restrictions would require another model.

Further references