6. Let B(t) be a Brownian motion on (2, F, P) and tF(t) be a fltration for B(t). Suppose that a stock price follows dS(t)rS (t)dt oS (t)dB (t) where r is the interest rate. Consider an agreement (made at t) to pay a specified price K(t) at time T(> t) for a share of stock. Determine the price K (t) which makes the value of this contract be zero at time t. (Hint: Specify the payoff at time T and find the value of the contract at time t by using the risk-neutral measure. 6. Let B(t) be a Brownian motion on (2, F, P) and tF(t) be a fltration for B(t). Suppose that a stock price follows dS(t)rS (t)dt oS (t)dB (t) where r is the interest rate. Consider an agreement (made at t) to pay a specified price K(t) at time T(> t) for a share of stock. Determine the price K (t) which makes the value of this contract be zero at time t. (Hint: Specify the payoff at time T and find the value of the contract at time t by using the risk-neutral measure