Question 793 option, hedging, delta hedging, gamma hedging, gamma, Black-Scholes-Merton option pricing
A bank buys 1000 European put options on a $10 non-dividend paying stock at a strike of $12. The bank wishes to hedge this exposure. The bank can trade the underlying stocks and European call options with a strike price of 7 on the same stock with the same maturity. Details of the call and put options are given in the table below. Each call and put option is on a single stock.
| European Options on a Non-dividend Paying Stock | |||
| Description | Symbol | Put Values | Call Values |
| Spot price ($) | S0 | 10 | 10 |
| Strike price ($) | KT | 12 | 7 |
| Risk free cont. comp. rate (pa) | r | 0.05 | 0.05 |
| Standard deviation of the stock's cont. comp. returns (pa) | σ | 0.4 | 0.4 |
| Option maturity (years) | T | 1 | 1 |
| Option price ($) | p0 or c0 | 2.495350486 | 3.601466138 |
| N[d1] | ∂c/∂S | 0.888138405 | |
| N[d2] | N[d2] | 0.792946442 | |
| −N[−d1] | ∂p/∂S | -0.552034778 | |
| N[−d2] | N[−d2] | 0.207053558 | |
| Gamma | Γ=∂2c/∂S2 or ∂2p/∂S2 | 0.098885989 | 0.047577422 |
| Theta | Θ=∂c/∂T or ∂p/∂T | 0.348152078 | 0.672379961 |
Which of the following statements is NOT correct?
Question 956 option, Black-Scholes-Merton option pricing, delta hedging, hedging
A bank sells a European call option on a non-dividend paying stock and delta hedges on a daily basis. Below is the result of their hedging, with columns representing consecutive days. Assume that there are 365 days per year and interest is paid daily in arrears.
| Delta Hedging a Short Call using Stocks and Debt | |||||||
| Description | Symbol | Days to maturity (T in days) | |||||
| 60 | 59 | 58 | 57 | 56 | 55 | ||
| Spot price ($) | S | 10000 | 10125 | 9800 | 9675 | 10000 | 10000 |
| Strike price ($) | K | 10000 | 10000 | 10000 | 10000 | 10000 | 10000 |
| Risk free cont. comp. rate (pa) | r | 0.05 | 0.05 | 0.05 | 0.05 | 0.05 | 0.05 |
| Standard deviation of the stock's cont. comp. returns (pa) | σ | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 |
| Option maturity (years) | T | 0.164384 | 0.161644 | 0.158904 | 0.156164 | 0.153425 | 0.150685 |
| Delta | N[d1] = dc/dS | 0.552416 | 0.582351 | 0.501138 | 0.467885 | 0.550649 | 0.550197 |
| Probability that S > K at maturity in risk neutral world | N[d2] | 0.487871 | 0.51878 | 0.437781 | 0.405685 | 0.488282 | 0.488387 |
| Call option price ($) | c | 685.391158 | 750.26411 | 567.990995 | 501.487157 | 660.982878 | ? |
| Stock investment value ($) | N[d1]*S | 5524.164129 | 5896.301781 | 4911.152036 | 4526.788065 | 5506.488143 | ? |
| Borrowing which partly funds stock investment ($) | N[d2]*K/e^(r*T) | 4838.772971 | 5146.037671 | 4343.161041 | 4025.300909 | 4845.505265 | ? |
| Interest expense from borrowing paid in arrears ($) | r*N[d2]*K/e^(r*T) | 0.662891 | 0.704985 | 0.594994 | 0.551449 | ? | |
| Gain on stock ($) | N[d1]*(SNew - SOld) | 69.052052 | -189.264008 | -62.642245 | 152.062648 | ? | |
| Gain on short call option ($) | -1*(cNew - cOld) | -64.872952 | 182.273114 | 66.503839 | -159.495721 | ? | |
| Net gain ($) | Gains - InterestExpense | 3.516209 | -7.695878 | 3.266599 | -7.984522 | ? | |
| Gamma | Γ = d^2c/dS^2 | 0.000244 | 0.00024 | 0.000255 | 0.00026 | 0.000253 | 0.000255 |
| Theta | θ = dc/dT | 2196.873429 | 2227.881353 | 2182.174706 | 2151.539751 | 2266.589184 | 2285.1895 |
In the last column when there are 55 days left to maturity there are missing values. Which of the following statements about those missing values is NOT correct?