SQL Server Operating system error 5: "5(Access is denied.)"

I am starting to learn SQL and I have a book that provides a database to work on. These files below are in the directory but the problem is that when I run the query, it gives me this error:

Msg 5120, Level 16, State 101, Line 1 Unable to open the physical file "C:\Murach\SQL Server 2008\Databases\AP.mdf". Operating system error 5: "5(Access is denied.)".

   CREATE DATABASE AP
      ON PRIMARY (FILENAME = 'C:\Murach\SQL Server 2008\Databases\AP.mdf')
      LOG ON (FILENAME =     'C:\Murach\SQL Server 2008\Databases\AP_log.ldf')
      FOR ATTACH
    GO

In the book the author says it should work, but it is not working in my case. I searched but I do not know exactly what the problem is, so I posted this question.

SQL Server database engine service account must have permissions to read/write in the new folder.

Check out this

To fix, I did the following:

Added the Administrators Group to the file security permissions with full control for the Data file (S:) and the Log File (T:).

Attached the database and it works fine.