dont understand problem.

semidevil

if X1 is a poisson random variable for which E(X1) = lambda, and if the conditional pdf of X2 is given that X1 = x1 is a binomial w/ parameters x1 and p, show that the marginal pdf of X2 is a Posson w/ E(X2) = lambda * p.


first, can someone decipher the question for me? I dotn even know what it is saying, and dont have any idea how to start at all.....

any hints, or is there an easier way to rephrase this question?