Fill in the blanks to make each of the following a true statement :

$A \cap A^{\prime}=\ldots$

If $A$ and $B$ be any two sets, then $(A \cap B)'$ is equal to

Let $U=\{1,2,3,4,5,6,7,8,9\}, A=\{1,2,3,4\}, B=\{2,4,6,8\}$ and $C=\{3,4,5,6\} .$ Find

$B^{\prime}$

If $n(U)$ = $600$ , $n(A)$ = $100$ , $n(B)$ = $200$ and $n(A \cap  B )$ = $50$, then $n(\bar A  \cap \bar B )$ is 

($U$ is universal set and $A$ and $B$ are subsets of $U$)

Taking the set of natural numbers as the universal set, write down the complements of the following sets:

$\{ x:x$ is an odd natural number $\} $