As part of your internship project, you are asked to analyze the performance of a local CVS store’s checkout process during the lunch hour, i.e., 12PM–1PM. During this period, there is an average of 60 customers per hour arriving at the checkout area. Currently, there are three waiting lines, one for each of the three checkout counters, each can serve at most one customer at a time and the first arriving customer is served first. Assume that customers are equally likely to join each of the three lines for the checkout counters and that there is no bulking, negating, or jockeying. The standard deviation of the inter-arrival time to each waiting line is 6 minutes. On average it takes 2 minutes (coefficient of variation = 1) to serve a customer. What is the average time in system (in second) for the customers?