Because it is a parallelogram, AD=BC AB=DC ∠A=∠C ∠B=∠D Because E and F are the midpoint between AB and DC, AE=FC.

So △AED=△CFB

So Germany =FB and ∠ Ade =∠CBF, so ∠MDF=∠NBE =BF.

Because m and n are the midpoint of de and FB, MD=NB ME=FN.

△DMF=△BNE because FC=AE and EB=DF.

So MF=NE

So the equilateral quadrilateral is a parallelogram, so the quadrilateral MFNE is a parallelogram.

Hope to adopt