As Shown in the Figure, a Man Is Traveling on a Bicycle

As shown in the figure, a man is traveling on a bicycle along a straight road that runs
parallel to and right next to some railroad tracks. While moving at 10 m/s, he hears the
whistle of a train that is behind him, as shown in the figure. The frequency emitted by the
train's whistle is 820 Hz, but the frequency the man hears is 774 Hz. The speed of sound is
340 m/s.
(a) What frequency is heard by a stationary observer located between the train and the
bicycle?
(b) What is the speed of the train, and is the train traveling away from or toward the
bicycle?