Show / Hide Document Category & Display the total Quantity

Question

I have three column in a SharePoint Document Library.
1st column name is Category (To category IT books)
2nd column name is Title (The title of the IT books)
3rd column name is Quantity (It display how many people wants to buy this particular book)

May I know how I can display the total quantity based on the category and display the total quantity for each category?
and also how do I show those category that I want ~or~ hide those category that I do not want?

Answer 1

Create filtered views in the document library including a sum on the quantity field as needed.