8. S1 and S2 are random variables representing total claim amounts in two portfolios, and both can be well modeled by compound Poisson distributions. S1 = Y1 + ... + YN1 where N1 is Poisson with parameter lambda1 = 2 and the claim size random variable Y has a distribution given by Y = { 200 prob = 0.5, 300 prob = 0.3, 400 prob = 0.2. Similarly, S2 = Z1 + ... + ZN2 where N2 is Poisson with parameter lambda2 = 3 and the claim size random variable Y has a distribution given by Z = { 300 prob = 0.1, 400 prob = 0.3, 500 prob = 0.6. If S1 and S2 are independent, what is the probability distribution of S = S1 + S2? What are its mean, variance and moment generating function? What is P[S <= 400]? Use the recursive formula to find P[S = r] for r <= 2000.