A boatman is at which is 4.51cm from the nearest point B on A straight shore. He wishes to reach in Minimum time a point C. Situated on the shore 9km from B. How far from C should He land if He can now at the rate of 6kph and walk at the rate of 7.5kph.

I'm lazy...you can find the answer in this link:

A boatman is at which is 4.5 kilometers