I have been posed the question

The crests of rollers directly following a ship 67m long overtake it at intervals of 16.5 sec. It takes a crest 6 sec to traverse the length of the ship.

Find the wave length of the rollers and the speed of the ship?

Im stuggling to find where to even start. I know that the wave length is given by (2pi/k) where k is the wave number not sure if this helps