The relationship between the speed, the frequency and the wavelength of a wave is given by:
[tex]f= \frac{v}{\lambda} [/tex]
where
f is the frequency
v is the speed of the wave
[tex]\lambda[/tex] is its wavelength
for the pressure wave in this problem, [tex]\lambda=2.5 m[/tex] and v=1400 m/s, therefore its frequency is
[tex]f= \frac{v}{\lambda}= \frac{1400 m/s}{2.5 m}=560 Hz [/tex]
