A risky asset has value 4, at time r. A probability measure R is defined so that Ay is an R-martingale, where v is calculated using the risk-free interest rate. Explain why R can be described as a risk-neutral probability measure. [2] (ii) Let X, =vE [CF,], where C is a discrete random variable occurring at time T>1. Prove that X, is an R-martingale. [2] Hint: if X is a discrete random variable and Y is a vector of random variables, then E[E[XIX]]-E[X]. (ii) Stating any results that you use, deduce that , is previsible, where dX, 8,dD,, where D, AV. - = [2]