3. Let X1 = M1 + M2 + ... + MN be a random variable with M; are i.i.d. random variable, M1, M2, ..., N are independent, where N ~ Poisson() = 2) and Mi ~Poisson() = 4); X2 be a random variable characterized by a mixed Poisson distri- bution with the mixing distribution defined by the pdf fA(x) = 1 2re ba for x > 0 and 0 otherwise; X3 be a random variable characterized by a mixed Poisson distribution with the mixing distribution defined by the pdf fA(x) = 16xe-4 for x > 0 and 0 otherwise, where X1, X2 and X3 are independent. If X = X1 + X2 + X3, calculate P(X = 3)