a service manager at a call center monitors the number of calls from customers who are not happy with the service of a specific vendor. During a 10-day period, the number of daily calls from customers who were not happy with this vendor were recorded. These numbers are 9, 6, 3, 8, 1, 6 7, 4, 8, and 8. What are the 3-sigma upper and lower control limits for the number of daily complaints