A medium-sized company uses a backup strategy that includes a full backup every Sunday at 2:00 AM and differential backups Monday through Saturday at 2:00 AM. The backups are written to a network-attached storage (NAS) device. On Thursday morning, the company experiences a ransomware attack that encrypts all data on the file server, including the NAS. The administrator needs to restore the file server with minimal data loss. The last successful full backup was from the previous Sunday, and differential backups were successful on Monday, Tuesday, and Wednesday. However, Thursday's differential was not completed because the attack occurred before the scheduled time. The administrator attempts to restore using the Sunday full backup and Thursday's differential, but the restore fails because the differential backup on the NAS is also encrypted. Which of the following is the best course of action?