Testing for coplanarity can be done by finding the point-plane distances of the points , ..., from the plane determined by and checking if they are all zero, by using arbitrary number of points , ..., . Two lines will not always share all planes, though. They can be coplanar on the same horizontal plane, for example, but not be on the same vertical plane.
In this problem, we can see that the line WY is obviously in both planes, and there won't be any additional points unless the planes are coincident. In this case, since W, X, Y and Z are not all coplanar, the planes don't coincide, so the answer is Line WY.
