Can you solve the MAGNET RIDDLE? ft YouTube CEO Susan Wojcicki

Take the file you mentioned,  
File a small amount off from one of the bars onto a sheet of paper from your office filing cabinet ( is that where you keep the file? Lol) 
Take the same bar and hold it under the paper with the filings on it to see if the filings move..  If they move,  that's the magnetic bar,  and if not then the other bar is the magnet.