Vectors in Space · Medium problem

A bead can slide only along a straight wire pointing in the direction $\mathbf u = (3, 4, 0)$. A force $\mathbf w = (9, 2, 6)$ newtons is applied to the bead. Only the component of $\mathbf w$ perpendicular to the wire presses against it (the wire supplies an equal and opposite normal force to keep the bead on track, which determines the friction). Find the magnitude of that perpendicular component.