Hi there, I have no idea how to do this problem. Please help me. Thanks in advance. Thanks a lot!!!

1. An efficient packing of the discs is obtained by dividing the metal sheet into hexagons and cutting the circular lids and bases from the hexagons. Show that if this method is used, then the amount of metal used is minimized when h/r = (4 square-root of 3)/ pi= 2.21.