Preston says the sequence of transformations that maps triangle ABC onto triangle DEF is: rotate it 180 degrees about the origin, and then translate it up 7 units. Chanel says the sequence of transformations that maps triangle ABC onto triangle DEF is: reflect it across the x-axis, then reflect it across the y-axis, and then translate it up 6 units and left 1 unit. Whose sequence proves triangle ABC is congruent to triangle DEF? Why?