Skip to content

Stock-weighted call payoff in Black-Scholes

Question

Work in the Black-Scholes model with rate rr and volatility σ\sigma. A contract pays at time TT the amount STmax⁡(ST−K,0)S_T\max(S_T-K,0), that is, the stock price multiplied by a call payoff. Find its price in closed form.

Short answer

S02e(r+σ2)TN(d1+σT)−KS0N(d1)S_0^2e^{(r+\sigma^2)T}N(d_1+\sigma\sqrt T)-KS_0N(d_1), with d1d_1 the usual Black-Scholes d1d_1. Split the payoff into ST21ST>K−KST1ST>KS_T^2\mathbf 1_{S_T>K}-KS_T\mathbf 1_{S_T>K}. The second piece is KK asset-or-nothing calls worth KS0N(d1)KS_0N(d_1); the first uses E[ST2]=S02e(2r+σ2)T\mathbb E[S_T^2]=S_0^2e^{(2r+\sigma^2)T} and a change of measure that shifts the log-drift by 2σ22\sigma^2.

Adapted from Joshi, Denson & Downes, Quant Job Interview Questions and Answers, Q2.7, p.17; question and answer rewritten by SelfMadeQuant.com.

See the hint and the full worked solution in the question bank (free account).

Open the worked solution

Lessons behind this question

Start with a free lesson: Options is part of a free topic. Create a free account, no card needed, to read it in full with worked solutions.

Read it free