The snapshot and history graphs for a wave are given below. What is the wave speed?

The snapshot and history graphs for a wave are given below. What is the wave speed? Recall that positive speeds indicate a wave traveling to the right, and negative speeds indicate a wave traveling to the left.
http://capa.phys.dal.ca/dalphysicslib/Graphics/Gtype35/snap5.2.gif
http://capa.phys.dal.ca/dalphysicslib/Graphics/Gtype35/snap5.2.gif