A helicopter drops a paratrooper carrying a buzzer that emits a 500 Hz signal. A sound receiver on the plane monitors the signal as the paratrooper...

A helicopter drops a paratrooper carrying a buzzer that emits a 500 Hz signal. A sound receiver on the plane monitors the signal as the paratrooper falls. If the perceived frequency becomes constant at 450 Hz, what is the terminal speed at the paratrooper ? Take the speed sound in air to be 343 m/s and assume the paratrooper always remains below the helicopter.