The number of DVDs is 80.

The factors form of .

The different ways Shannon arrange 80 DVDs on each self, at least 4 shelves of DVDs and at least 5 on each shelf as follows:

So, the CDs can be organized as 5 DVDs on 16 shelves.

So, the CDs can be organized as 8 DVDs on 10 shelves.

So, the CDs can be organized as 10 CDs on 8 shelves.

So, the CDs can be organized as 16 CDs on 5 shelves.

So, the CDs can be organized as 18 CDs on 4 shelves. \ \