Answer:
Δf=73Hz
Step-by-step explanation:
From the question we know that:
C = 1482 m/s
Vs = 0 m/s
Vr = -4.95 m/s (it's negative because it is in the opposite direction to the waves)
f0 = 22000 Hz
Applying the formula for the doppler effect:

f = 22073 Hz. So the difference is only 73Hz