Planning for a major redesign Beth collected data at her store on several consecutive Saturday mornings . She noticed that customers arrived at the checkout at a rate of approximately 100 per hour Fully 20 percent of the customers had 10 items or less Those people took about 2 minutes to serve on average , while customers with more than 10 items took about 4 minutes to process Beth expects service time to improve when new scanners are installed in the revised design Help Beth with her design for the system