algebra help

1). Doppler Effect TheDoppler effect (named after Christian Doppler) is the change in the pitch (frequency) of the sound from asource (s) as hard by an observer (o) when one or both are in motion. If we assume both te source and the observer are movng in the same direction, the relationship is
f'=fa(v-vo/v-vs)
where f' = prceived pitch by the observer
fa = actual pitch of the source
v = speed of sound in air ( assume 772.4 mph)
vo = speed of the observer
vs =speed of the source
Suppose you are traveling down the road at 45 mph and you hear an ambulance (with siren)coming toward you from the rear. The actual pitch of th siren is 600 hertz (Hz).
(a). Write a function f'(vs) that describes this scenario.
(b). If f' = 620 Hz, find the speed of the ambulance.

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