A street light is mounted at the top of a 5.4m pole. A man 1.8m tall walks away form the light in a straight path at a speed of 1m/s. How fast is the tip of his shadow moving when he is 10m from the pole?

note: visualise the shadow cast by the man as a horizontal line segment; the starting point of the segment is at the man's feet; the endpoint of the segment is what we call the tip of the shadow.

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I'm completely confused.

I'll be absolutely grateful for any help at all, no matter how small.

THANKS