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

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

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

$\{ x:x$ is a perfect cube $\} $

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

$\{ x:x\, \ge \,7\} $

Draw appropriate Venn diagram for each of the following:

$A^{\prime} \cup B^{\prime}$

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

${{\mathop{\rm U}\nolimits} ^\prime } \cap A =  \ldots $

Given $n(U) = 20$, $n(A) = 12$, $n(B) = 9$, $n(A \cap B) = 4$, where $U$ is the universal set, $A$ and $B$ are subsets of $U$, then $n({(A \cup B)^C}) = $