Answer:


Step-by-step explanation:
As per Doppler's effect of sound we know that when source and observer moves relative to each other then the frequency of sound observed by the observer is different from real frequency of sound.
As the source is moving here in this case so the frequency is given as

part a)
for lowest frequency we will have

here we know that
R = 54.6 cm

now we have


part b)
for maximum frequency we will have

here we know that
R = 54.6 cm

now we have

