4. Poisson Let 1" be the number of customers that arrive at a checkout counter during a given hour (note, 1' is the customers per hour). Assuming that 1" ~ Poitjri) is a Poisson random variable with J = 3. 41a. 1Write down the probability function pyv) for l' and clearlyr specify the values _v that Y may take. 4b. During a given hour, what is the probability that at most two customers arrive? 4c. let l"r :4! customers in first I minutes. We assume 1\