On a hot day in the desert (T = 48 degrees C), a sound of 320 Hz is emitted by a car travelling at 122 km/h toward a police officer.

On a hot day in the desert (T = 48 degrees C), a sound of 320 Hz is emitted by a car travelling at 122 km/h toward a police officer. If the sound frequency received by the police officer is 390 Hz, determine the speed of the police officer (in km/h).

Provide a positive answer if the police officer is travelling toward the speeding car or a negative answer if the police officer is travelling away from the speeding car.