Consider a 2-step binomial tree, with initial stock price being $10. For each time period, the stock price is expected to increase by 10% (when having an H) or decrease by 10% (when having a T). The interest rate Rm(n = 0,1,2), is given in the following binomial tree: P(H) R1(H)-5% H) P(T)=1/2 R,-4% 3 P(H)= Ri (T) = 3% P(7)I 3 R2(TT)-2% Calculate the value of an American put option with strike price K = 11, and write down the optimal exercising time for this derivative. (Notethe risk neutral probability,may be different for each step.)