How much disk space is available to the operating system?

A server has the following configuration:

– 5x 1 TB drives configured in a RAID 5 array

– 1x 1 TB as a global hot spare

– Persistent Hot Spare Slot enabled

A user adds one additional 2 TB drive to the existing array using RAID migration.

How much disk space is available to the operating system?
A . 5 TB
B . 6 TB
C . 7 TB
D . 8 TB