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Question 1
a) Assume an underlying Black–Scholes model with σ > 0, r > 0, S0 > 0 and without dividend payments. Formulate a partial differential equation that is satisfied by the price V of the European down-and-in barrier call option with barrier B and strike K, where K > B, and where V (t, S) is a function of current time t and stock-value S. Assume S0 > B. Indicate clearly the solution domain and the boundary conditions V (t, B) and V (T, S). b) Assume an underlying Black–Scholes model with σ > 0, r > 0, S0 > 0 and without dividend payments. Determine the linear complementarity problem for the American up-and-out put option with Barrier B and strike K, K < B, S0 < B. Indicate clearly the solution domain and the boundary condition at time T . c) Find the probability density function of Mt := sup0≤s≤tWs where (Wt)t≥0 is a standard Wiener process. Hint: Reflection principle. d) Let cfix(S,M, t,K) and pfl(S,M, t) denote the price function of a (European) fixed strike lookback call option and a (European) floating strike lookback put option respectively, where S is the time-t price of the underlying stock, M is the running maximum at time t and K is the strike price. Suppose M > K. Compute cfix(S,M, t,K)− pfl(S,M, t). Hint: Consider a portfolio long in the call option and short in the put option. e) Compare the time-0 price of an up-and-out-call option with the price of a regular call option with same strike and same maturity. Hint: In-out-parity. 1 Question 2 (25 marks) Assume a Black–Scholes model with drift µ ∈ R, risk-free rate r > 0, initial value S0 > 0 and volatility σ > 0 and assume the stock does not pay any dividends. Suppose the arbitrage-free price at time t with 0 ≤ t ≤ T of an up-and-out barrier call option with barrier B > S0 and strike K > 0 is given by V (t, St), where St denotes the value of the underlying asset at time t. (a) Formulate (without proof) a partial differential equation that is satisfied by V and explicitly state boundary conditions and the solution domain. (b) Express the arbitrage-free price at time 0 of an up-and-in barrier put option (with the same maturity T , same strike K and same barrier B as the up-and-out barrier call option) as a function of the following four quantities: • V (0, S0), • p: the price of a regular put option with strike K and maturity T , • buo: the price of an up-and-out option with payoff 1, barrier B and maturity T , • suo: the price of an up-and-out option with payoff ST , barrier B and maturity T . Question 3 (25 marks) Suppose we have two traded risky assets S (1) t and S (2) t , and one risk-free asset with Bt = e rt for r > 0. The dynamics of the risky assets under the real-world probability measure are given by dS (1) t = S (1) t µ1dt+ S (1) t σ1dW1,t dS (2) t = S (2) t µ2dt+ S (2) t σ2dW2,t dW1,tdW2,t = ρdt where W1,t and W2,t are two correlated Wiener processes, µ1, µ2 ∈ R denote the drifts of the processes, σ1, σ2 > 0 denote the volatilities of the first and second asset and where ρ ∈ [−1, 1]. Find the arbitrage-free price at time 0 of a financial derivative with payoff φ(S (1) T , S (2) T ) at maturity T , where φ(S (1) T , S (2) T ) := S (1) T 1 { S (2) T ≤KS (1) T } for K > 0. Question 4 (25 marks) A down-and-in cash call is a claim that pays 1 at maturity date T > 0 provided the barrier B is hit and that ST ≥ K. Suppose B ≤ K. Assume an underlying Black–Scholes model with σ > 0, r > 0, S0 > 0 and without dividend payments. Compute the price at time 0 of a down-and-in cash call. Hint: Apply the reflection principle to the log-price process, similar to the approach from Lecture 10. You may use the results from the lecture without proof.