A train whistle produces a sine wave with a wavelength of 0.7841 m in air when the speed of sound is 345 m/s. As the train is approaching you from far away, you are standing near the track when you hear a sound with a frequency of 523.25 Hz.
(a) What is the train's speed relative to you?
(b) What frequency do you hear after the train passes you?
(c) A second identical train is trying to catch up to the first. After it passes you, it blows its whistle at the same time as the first train is blowits whistle, causing you to hear a beat frequency of 10.0 Hz. What is/are the speed(s) of the second train relative to you?