A car is accelerating while its horn is sounding. Just after the car passes a stationary person, the person hears a frequency of 1004.8 Hz. Sixteen seconds later, the frequency heard by the person has decreased to 1002.8 Hz. When the car is stationary, its horn emits a sound whose frequency is 9.90 102 Hz. The speed of sound is 343 m/s. What is the acceleration of the car?