Mulder will read the files on ninenine unsolved cases from a list of fourteenfourteen. he does not care about the order in which he reads the files.

Since the order of the selection of files does not matter, this is the concept of combination not permutation.
therefore suppose we want the combination of 5 files that can be selected from 14. This will be given by:
14C5
=(14!)/(9!3!)
=2002
We therefore conclude that there are 2002 ways that 5 files can be selected from 14 files;