A cop car moving at a speed of 36.1 m/s emits a siren whose built-in frequency is 820 Hz. You are driving at a speed of 42.2 m/s. The speed of sound in air is 343 m/s. What is the observed frequency of the siren when you are driving towards the cop car?
1) 820 Hz
2) 860 Hz
3) 880 Hz
4) 900 Hz
