Help me with my calculus problem . Please be hurry !?

A boat is 4 miles from the nearest point on a straight shoreline ( call it point A )

Then a restaurant is on the shoreline , and 6 miles away from A .

A woman plans to row to appoint on shore , and then walk to the restaurant . If she can walk at 3 mph , at what speed must she be able to row so that the quickest way to get to the restaurant is to row directly .

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