An ambulance is rushing to a hospital and its siren emits a sound at a frequency of 750 Hz. The ambulance is moving at a speed of 33 m/s towards a stationary observer on the sidewalk. The speed of sound in air is approximately 340 m/s. Calculate the frequency of the siren as heard by the stationary observer.

An ambulance is rushing to a hospital and its siren emits a sound at a frequency of 750 Hz. The ambulance is moving at a speed of 33 m/s towards a stationary observer on the sidewalk. The speed of sound in air is approximately 340 m/s. Calculate the frequency of the siren as heard by the stationary observer.