The segmant line AB with endpoints A(6,2,-4) and B(6,2,0) is rotated so that the image of A is A(-6,-2,-4) and?

the image of B is B(-6,-2,0) About which axis was line AB rotated to get line A'B'? im not sure if this makes any sense to anyone bt it looks lke jibrish too me if u can help please if not just skip it...