If $A=\{3, 5, 7, 9, 11\}$,$B=\{7, 9, 11, 13\}$,$C=\{11, 13, 15\}$,and $D=\{15, 17\}$; find $(A \cup D) \cap (B \cup C)$.

Find the union of each of the following pairs of sets:
$A = \{1, 2, 3\}, B = \varnothing$

If $A = \{ x : x \text{ is a natural number} \}$,$B = \{ x : x \text{ is an even natural number} \}$,$C = \{ x : x \text{ is an odd natural number} \}$,and $D = \{ x : x \text{ is a prime number} \}$,find $A \cap B$.

Which Venn diagram represents the truth of the statement "No child is naughty"?
Where $U$ = Universal set of human beings,$C$ = Set of children,$N$ = Set of naughty persons.

Which Venn diagram represents the truth of the statement "All students are hard working."
Where $U$ = Universal set of human beings,$S$ = Set of all students,$H$ = Set of all hard workers.

Let $A$ and $B$ be two sets such that $n(A) = 0.16$,$n(B) = 0.14$,and $n(A \cup B) = 0.25$. Then $n(A \cap B)$ is equal to: