Can someone help explain each step to solve? I'm trying to teach myself and I don't know where to start with this one. Thank you!

The random variable / has a Poisson(A) distribution if P(N = k) = k E {0, 1, 2, 3, . . .). k! It turns out that E[N] = Var(N) = A. Show that when making random, independent observations Yl.... . Y,, from a Poisson distribution with mean A that the maximum likelihood estimator for A is the sample mean: AyLy = 1