$A, B$ and $C$ are subsets of universal set $U$. If $A=\{2,4,6,8,12,20\}, B=\{3,6,9,12,15\}$; $C=\{5,10,15,20\}$ and $U$ is the set of all whole numbers, draw a Venn diagram showing the relation of $U, A, B$ and C.