Identify the rotation rule on a coordinate plane that verifies that triangle a(2,-1), b(4,1), c(3,3) and triangle a'(-2, 1), b'(-4,-1), c'(-3,-3) are congruent when rotated 180°. a) (x, y) → (-y, x) b) (x, y) → (-x, -y) c) (x, y) → (y, -x) d) the triangles are not congruent