A train is moving parallel to a highway at 20 m/s. A car is travelling in the same direction as the train at 40 m/s. The car horn sound at 510 Hz and the train whistle sound at 320 Hz.
(a.) When the car is behind the train what frequency does an occupant of the car observe for the train whistle?
(b.) when the car is in front of the train what frequency does a train passenger observe for the car horn just after passing?