Triangle CDA is the image of triangle ABC after a 180º rotation around the midpoint of segment AC. Triangle ECB is the image of triangle ABC after a 180º rotation around the midpoint of segment BC. Quadrilateral A B D E. Point C lies on D E. Segments A C and A B are drawn inside the quadrilateral and each have a point marked. Explain why ABCD and ABEC are parallelograms.