In △FDP and
△ADB,
∠ADB=∠FDP (Common angle)
∠DAB=∠DFP (Corresponding angles)
∠DBA=∠DPF (Corresponding angles)
Thus, △FDP∼△ADB (AAA rule)
hence, FPAB=FDAD
FPAB=12 (Since, AF = FD)
or FP=12AB...(I)
Since, AB∥FB∥CD
By equal Intercept theorem, BE=EC
Hence, PE=12CD ...(II)
Thus, adding I and II
PF+PE=12(AB+CD)
2EF=AB+CD