3. (a) (2 pts) For XPois(), find E[X!] (the average factorial of X ), if it is finite. (b) (2 pts: Sum of independent Poissons: convolution property) Use the Law of total probability to show that if XPois( 1),YPois(2), and X is independent of Y, then X+Y Pois(1+2).
3. (a) (2 pts) For XPois(), find E[X!] (the average factorial of X ), if it is finite. (b) (2 pts: Sum of independent Poissons: convolution property) Use the Law of total probability to show that if XPois( 1),YPois(2), and X is independent of Y, then X+Y Pois(1+2).