If $A$ and $B$ are 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:

Consider the following relations:
$(1) \, A - B = A - (A \cap B)$
$(2) \, A = (A \cap B) \cup (A - B)$
$(3) \, A - (B \cup C) = (A - B) \cup (A - C)$
Which of these is/are correct?

If $A = \{1, 2, 3, 4\}$,$B = \{3, 4, 5, 6\}$,$C = \{5, 6, 7, 8\}$,and $D = \{7, 8, 9, 10\}$,find $A \cup B$.

If $A = \{1, 2, 3, 4\}, B = \{3, 4, 5, 6\}, C = \{5, 6, 7, 8\}$ and $D = \{7, 8, 9, 10\}$,find $B \cup D$.

If sets $A$ and $B$ are defined as follows:
$A = \{(x, y) : y = \frac{1}{x}, 0 \neq x \in R\}$
$B = \{(x, y) : y = -x, x \in R\}$,then

Let $A = \{a, b, c\}, B = \{b, c, d\}, C = \{a, b, d, e\}$. Then $A \cap (B \cup C)$ is