Since 84 shoppers per hour make a purchase, 84 shoppers per hour enter the checkout line. However, this needs to be converted to the number of shoppers per minute (in order to be used with T=5). Since there are 60 minutes in one hour, the rate is 84shoppersperhour
60minutes
=1.4 shoppers per minute. Using the given formula with r=1.4 and T=5 yields