Let \( A \) and \( B \) be two distinct points on the line \( L : \frac{x-6}{3}=\frac{y-7}{2}=\frac{z-7}{-2} \). Both \( A \) and \( B \) are at a distance \( 2\sqrt{17} \) from the foot of perpendicular drawn from the point \( (1,2,3) \) on the line \( L \). If \( O \) is the origin, then \( \overrightarrow{OA}\cdot\overrightarrow{OB} \) is equal to:
