A 520-Hz Whistle Is Moved Toward a Listener at a Speed

Multiple Choice

A 520-Hz whistle is moved toward a listener at a speed of 50 m/s.At the same time,the listener moves at a speed of 70 m/s in a direction away from the whistle.What is the apparent frequency heard by the listener? (The speed of sound is 340 m/s. )

A) 444 Hz
B) 484 Hz
C) 735 Hz
D) 360 Hz
E) ​610 Hz