Two train whistles, A and B, each have a frequency of 392 Hz. A is stationary and B is moving toward the right (away rom A) at a speed of 35.0 m/s. A listener is between the two whistles and is moving toward the right with a speed of 15.0 m/s. No wind is blowing.
a) what is the frequency from A as heard by the listener?
b) what is the frequency from B as heard by listener?
c) what is the beat frequency detected by the listener?