In triangle XYZ, points L, M and N are the midpoints of sides XY, XZ and YZ respectively.
(i) Prove that quadrilateral YLMN is a parallelogram.
(ii) Show that the area of quadrilateral YLMN is exactly half the area of triangle XYZ.
(iii) If XY=8cm, XZ=10cm and YZ=12cm, find the perimeter of quadrilateral YLMN."