I'm stuck on a Calculus Related Rates question.

A rotating beacon is 5 miles out in the water.

Point A is a point on the shore closest to the beacon.

The beacon rotates at 7 rev/min sweeping a beam of light down the shore each time.

How fast (in miles/min) is the point where the beam hits the shore moving at an instant when the beam is lighting up a point 5 miles along the shore from point A?

The answer is given as 439.82