In a fast-food restaurant, the manager observes that the average inter-arrival time between customers is three minutes with a standard deviation of four minutes. The service time for a customer is four minutes with a standard deviation of five minutes. At present, they have two servers processing an order. What is the average wait time per customer in minutes? If the manager wants the wait time to be less than a minute, then at a minimum, how many servers should be deployed?

Please help explain and show with an excel sheet and formulas