Question 29
In a plane rectangular coordinate system $xOy$, points $A$, $B$ are on the parabola $y^2 = 4x$, satisfying $\vec{OA} \cdot \vec{OB} = -4$, and point $F$ is the focus of the parabola. Then $S_{\triangle OFA} \cdot S_{\triangle OFB} = \_\_\_\_\_\_$.