Let Yn:=k=0nSk for n=0,,N in the N-period binomial model. An Asian call option with strike K and maturity N pays VN:=(N+11YNK)+at time N. Let Vn be the arbitrage-free price of the option at time n,n=0,,N. a) Show that we have Vn=vn(Sn,Yn) for a suitable function vn(s,y) for all n=0,,N, and express vn in terms of vn+1. b) Let N=2 and S0=4,u=23,d=21,r=0. Compute the price V0 of the Asian call option with strike K=4 and maturity 2