i just started stats uni this year so stats is completely new to me. can someone please help me with this question which i'm sure must be really easy, but i dont understand a thing!

Suppose that X has a poisson distribution with mean lamda.

a) find by summation the mean of X

b) find also the variance of X

If W is a poisson random variable with mean 2, what is P(W>3 given W>1) ?

[for this question we have to use the tables right? and not the equation?)

If x1 = 3 ; x2 = 2 ; x3 = 4 ; x4 = 2 ; x5 = 5, and all are equally likely values for X, what is E[X(X-1)] ?

thanks so much...