The relationship between the speed, the frequency and the wavelength of a wave is given by:

where
f is the frequency
v is the speed of the wave

is its wavelength
for the pressure wave in this problem,

and v=1400 m/s, therefore its frequency is
Answer:
If the height is in metres, the speed is 24.25m/s
Answer: C. 20J
Explanation: im pretty sure sorry if im wrong :(