MCSA Interview Question:

You have a server named Server1 that runs Windows Server 2003 Service Pack 2 (SP2).You perform a normal backup of Server1 every Saturday. You need to implement a backup strategy for Server1 to meet the following requirements:
Minimize the time required to restore files.
On weekdays, back up only files that have changed since the Saturday backup.
Which type of backup should you perform on weekdays?