4. Two plane mirrors of length L are separated by distance L and a man M₂​ is standing at distance L from the connecting line of mirrors as shown in the figure. A man M₁​ is walking in a straight line at distance 2 L parallel to mirrors at speed u, then man M _​2 ​ at O will be able to see image of M ₁ for time:



$$\begin{gathered} \left(A\right) \frac{4L}{u} \\ \left(B\right) \frac{3L}{u} \\ \left(C\right) \frac{6L}{u} \\ \left(D\right) \frac{9L}{u} \end{gathered}$$

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