The Calculus Conundrum

After receiving six Outstanding N.E.W.T.s, Draco is a well-respected potions master who frequently publishes articles in academic journals, winning several awards. Harry even teases Draco by asking him if there's anything he doesn't know in that smart brain of his. However, Draco is only human and it turns out that even a calculus problem can baffle the smartest of wizards.