In retail outlets, customers are usually processed on a first come, first served basis. Why? Is the express lane in the supermarket an exception? Craft a sequencing rule to explain express lane behaviour.

First Come

A principle where services or resources are allocated to recipients in the order of their arrival or request.

First Served

First served, traditionally known as "first come, first served," is a service principle where customers are attended to in the order of their arrival or request.

Express Lane

A designated checkout lane in supermarkets for customers with a small number of items, designed to speed up the shopping process.