Please help with this question. Please provide all steps and calculations. Please don't use answers from other websites, I looked at them and didn't understand them. Thank you

Problem 4. Let X1, X2, ... be i.i.d. random variables. Each Xi follows Exponential (1) with the pdf fx(x) = de-Ax, x 2 0. Let N follow Poisson()). Suppose N is independent of the Xi's. Let S = Zil Xi.(1). Derive the expected value of S. (2). Derive the variance of S. (3). Derive the covariance between S and N. (4). Derive the moment generating function of S