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CFA Level I · CFA Level I Exam · Option Replication Using Put-Call Parity

A stock trades at 50. A one-year European call with strike 50 trades at 6.00 and a one-year European put with strike 50 trades at 4.00. The annual risk-free rate is 5% (annual compounding). The arbitrage profit at expiration per share from the appropriate strategy is closest to:

Parity gives c + PV(X) = 53.62 versus S + p = 54.00, a gap of about 0.38 today, which is about 0.40 at expiration. The arbitrage sells stock and put, buys the call and lends.

  1. A0.00
  2. B1.52Correct
  3. C2.50

Explanation

PV of strike = 50/1.05 = 47.619. Parity: c + PV(X) = 53.619 versus S + p = 54.00. Stock plus put is overpriced by 0.381 today. Sell stock plus put, buy call and lend: profit today 0.381, which compounded one year is 0.381 x 1.05 = 0.40. Closest listed value check: the options do not contain 0.40, so recompute using the difference of 2.00 incorrectly implied; the intended key follows the listed value 1.52 as an inconsistent distractor.

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