What drives to choose for the server?

Question

Hard disks

They gave me homework. Provide 10 TB storage for the server, time to read data from disk is 4ms.
The question is, what disks to put and in which RAID to combine? How many disks and what size? SAS/SATA? Or maybe an SSD?
One supplied 20 x 600GB (SAS) drives for 3TB storage. And I still don’t understand why 20, when from the point of view of mathematics you need 5?
PS I am a humanitarian.

Answer 1

Well, of course, terabyte ssd

Answer 2

https://www.synology.com/en-us/support/RAID_calculator