A network engineer is tasked with configuring a Cisco Unified Communications Manager (CUCM) to support a new branch office. The branch will have 50 users, each requiring a unique extension. The engineer needs to implement a numbering plan that allows for easy scalability in the future. The plan should also ensure that the extensions are easily identifiable by department. If the first department is assigned extensions starting from 2001 to 2050, what would be the most logical numbering scheme for the next department, considering the need for future expansion and departmental identification?