Please solve the quesiton

Problem 4. You are interested in the hedging of an American put option written on a stock index with a continuous dividend payment. You are using a binomial tree for analyzing the put option and are given the following information. I Current price of the stock index is S = 31']. I The American put option expires in 4 periods. I The continuously compounded interest rate is r = [1.05 per period. I The continuous dividend yield rate is d = {LEI-1 per period. I The up and down stock index price movement per period is governed by u = 1.25 and d = llT. I The strike price is K = 23. {a} [5 points] Determine the optimal exercise strategy for the American put option. [This means that you indicate at which nodes in the tree you would exercise the put option. } {b} [5 points] \"What is the replicating portfolio (1'. e. the values of Li, 3]] at each of the three nodes at time 2'? (The three nodes at time 2 are {2,{1}, {2,1} and (2, 2} which are sometimes identied as corresponding to the movements dd, Lin and an respectively.)