A source and an observer are approaching one another with the relative velocity `40 ms^(-1)`. If the true source frequency is 1200 Hz, deduce the observed frequency under the following conditions:
(i) All velocity is in the source alone.
(ii) All velocity is in the observer alone.
The source moves in air at `100 ms^(-1)` towards the observer, but the observer also moves with the velocity `v_(0)` in the same direction.