1. A source of sound \(S\) emitting waves of frequency \(100\,Hz\) and an observer \(O\) are located at some distance from each other. The source is moving with a speed of \(19.4\,ms^1\) at an angle of \(60^\circ\) with the source observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air \(330\,ms^{−1}\)), is