Series of Wave Equation problem

[c4iscool]

A series of waves traveling at 200m/sec are being generated by a 50hz source. A point at the very top of the crest of a certain wave is ? meters away from a corresponding point 4 crests away.

The only equation I have is V=lambda*F. Is there a way to get the distance w/ this or am I missing something?

 

[Hootenanny]

HINT: Calculate the wavelength of the wave. For a crest to be four crests away how many wavelengths must they be apart?