A car is traveling on a street at 24.6 m/s. An ambulance is behind the car, moving in the same direction and with a speed of 38.7 m/s. The siren on the ambulance is emitting sound at a frequency of 1575 Hz. The speed of sound in the air is 343 m/s. A) What is the frequency of the siren heard by a person in the car? B) The driver of the car notices the ambulance, and slows down to 12.8 m/s. The ambulance passes the car and is moving away from the car. What frequency of the siren does a person in the car hear now?