"what is the most you can pay for the equipment and still have a positive npv? "

There are many benefits to using folders when working with lots of files.  Here are a few examples:

- You can use folders to sort your files by type, almost like drawers in a desk, so you might have folders for Music, Photographs, Documents, etc.

- You can use folders to group files together into a specific group.  For example in your Photographs folder you might have a folder titled BirthdayPhotographs for all the photographs from your birthday.

- As in the example above you can nest folders to create sub-categories.  Documents might include folders for Homework, Stories, Poems

- Folders can have different permissions applied to them, allowing you to keep personal files in a private folder only you can access, or secret files in a folder that doesn't show up in the normal list of folders!

The correct answer is "b".