Leo is planning the new backup strategy for a subsidiary his company is purchasing that does not currently have a backup strategy in place. He decides that a full backup should be run once per week. Once per day, everything that has changed since the last full backup will be archived. Once per hour everything that has changed since the last backup of any type will be backed up. Which of the following describes the backups that will be run every hour? a. Incremental b. Flexible c. Differential d. Variable