A vehicle, with a horn of frequency n is moving with a velocity of 30 m/s in a direction perpendicular to the straight line joining the observer and the vehicle. The observer perceives the sound to have a frequency (n+n1) . If the sound velocity in air is 300 m/s, then
a. n1=10n
b. n1=0
c. n1=0.1n
d. n1=−0.1n