The price of a non-dividend paying stock at time 1, S, is related to the price at time 0, So, as follows: S = us, with probability p and S =dS, with probability (1-p). The continuously compounded rate of return on a risk-free asset is r. (1) Derive an expression for the replicating portfolio for a European call option written on the stock that expires at time 1 and has a strike price of k, where dS < k