1. The problem statement, all variables and given/known data Let Y be the number of customers entering a ABC bank in a day. It is known that Y has a Poisson distribution with some unknown mean lambda. Suppose that 1% of the customers entering the branch in a day open a new ABC bank account. Find the mean and variance of the number of customers who open a new ABC bank account in a day. 2. Relevant equations 3. The attempt at a solution Just based on past experience, I THINK this is related to multivariate distributions and PROBABLY would use the fact E[E(Y|X)]=E(Y). But I am not sure how to define the random variables properly... Can someone explain? Thanks for any help!