Answer : The speed of the wave is 0.17 m/s
Explanation :
It is given that,
Wavelength of a wave, λ = 40 m
Time taken, t = 4 minutes = 240 seconds
Frequency,

Speed of the wave = frequency × wavelength
v = υ × λ

v = 0.167 m/s
or v = 0.17 m/s
The speed of the wave is 0.17 m/s
Hence, this is the required solution.