\textbf{166-} A person moves at a speed of 20 cm/s toward a flat mirror. The mirror is also moving at a speed of 20 cm/s toward the person. How many centimeters per second does the image move toward the person?
\hfill $80$ (1) \hfill $60$ (2) \hfill $40$ (3) \hfill $20$ (4) \hfill