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

I would use the file to make a little bit of iron powder from both the bars, now i'll have magnetic powder and not magnetic powder separated, then I'll drop some of each kind of powder on both rods one per time, if it stcks/follows the magnetic field arcs in both cases, that would be the magnet if that's the iron bar, only the magnetized powder will stick to it
(I hope my english was good, I am just a 15 years old Italian guy)