Pedant alert!
If you aren't 100% sure whether to use 'whom' or 'who' – please use (or utilise, if single syllable words cause you trauma) 'who'.
Pedant alert over.
If I remember my lessons well , you use whom , when it's preceded by a , "to." For instance , " To whom , do you wish me to give this plate . " Whom , is a person or people being acted upon . You use who , when they are the one(s) doing the action . As in , " Who made this beautiful artwork ? "