A stationary source is emitting sound ata fixed frequency $$f_0$$, which is reflected by two cars approaching the source. The difference between the frequencies of sound reflected from the cars is 1.2% of $$f_0$$. What is the difference in the speeds of the cars (in km per hour) to the nearest integer ? The cars are moving at constant speeds much smaller than the speed of sound which is 330 $$ms^{-1}$$.