Suppose that the stock price S, follows lognormal distribution St= Soe(a-8-0.50) t+oiz Prove that the conditional expectation of lognormal prices, when terminal stock price ST falls below Kis where d = d = E(ST ST < K) = Soe(a-s)r N(-d) N(-d) In(So/K) + (a-6 +0.50)T OVT In(So/K) + (a-8-0.50)T =d - oT Hints: E(ST ST < K) is defined as E(ST STK) = = E [ST1{ST