There is a source of sound (a tuning fork) moving towards a reflecting wall will a speed of 30 m s -1 . The velocity of the sound in air is 330 m s -1 and the frequency of the tuning fork is 600 Hz. The observer is between the source and the wall and is moving with some velocity V 1 towards the wall. The beat frequency heard by the observer is 4 Hz. If the tuning fork is waxed, the frequency beats heard by the observer becomes 3 Hz. If the new frequency of tuning fork is k then k / 50 is