D,E and F are respectively the mid-points of the sides BC, CA and AB of a ∆ABC. Show that (i) BDEF is a parallelogram. (ii) ar(∆DEF) = \frac { 1 }{ 4 } ar (∆ABC) (iii) ar(||gm BDEF) = \frac { 1 }{ 2 } ar(∆ ABC)