Two cars are approaching each other on a straight road and moving with a velocity of `30 kmh^(-1)`.if the sound produced in a car is of frequency 500 Hz, what will be the frequency of sound as heard by the person sitting in the other car ? When the two cars have crossed each other and are moving away from each other.what will be the frequency of sound as heard by the same person ? Speed of sound =`330 ms^(-1)`.