4. Two trains are moving away from each other. The first train travels at 180 kph while the second, 195 kph. The first train emits a sound of frequency 970 Hz. What is the frequency of the sound perceived by a passenger in the second train? 5. Two cars approach each other at different velocities. To warn the other driver, the driver on the first car (v=85 kph) blows his horn (1-750 Hz). After the driver on the first car's horn die out, the second driver blows his horn (f=845 Hz) and the driver from the first car perceives a sound with a frequency of 875 Hz. (a) What is the velocity of the second car? (b) What is the frequency of sound perceived by the second driver when the driver in the first car blew his horn