help pls
An observer moves to the left with some velocity, v, at the same time a sound wave source moves to the left with twice the velocity of the observer. How will the frequency of the source be shifted as it passes the observer?


The observed frequency will be greater than the source’s frequency.
The observed frequency will be less than the source’s frequency.
The observed frequency will be the same as the source’s frequency.
The source never passes the observer.