Evan is buying groceries at the supermarket. There are three open check-out lanes, and he wants to choose the lane that will allow him to pay and leave the supermarket as
soon as possible.
To estimate how long it will take to get through each line, Evan creates a model that
uses the following quantities:
• the number of carts and baskets waiting in line
• the total weight of the items in the carts and baskets waiting in line
• the total weight of the items in Evan's cart
• the average amount of time customers take to pay for their groceries
• the average amount of time it takes the cashier to scan an item
What other quantity does Evan need to know for his model to be useful?