Problem 5. Bob is on a train traveling at 80m/s. His friend Alice is on a train platform as Bob approaches. Bob sends continuous signal in the form of a 1/H z sound wave. a) What frequency will Alice measure as Bob approaches the platform? b) As Bob passes by and moves away from the platform, what frequency does Alice now measure? c) As Bob moves away from the platform, some of the sound waves bounce off the platform and return to him. What frequency does Bob measure for the returning signal? d) Another train is traveling next to Bob but moving more slowly at constant speed. Some of the sound reflects off of the other train and returns to Bob in the form of a 0.68/H z signal. How fast is the other train moving