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

if there is a non magnetic metal, just stroke that piece of metal with one of the bars. 
if it starts to stic k a little but, that bar is magnetic.

or make a makeshift compass. 

maybe if there is and old screen and you bring the bars close to it, one of the bars will distort the screen.

man, after think of 1 solution, the others kinda flow!