If $A$ and $B$ are not disjoint sets,then $n(A \cup B)$ is equal to

If $A$ and $B$ are any two events of a sample space,then the set-theoretic description for the event: "Exactly one of the events $A, B$ occurs" is
(Here $E^c$ denotes the complement of the event $E$)

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.

Consider the sets $A$ and $B$ where $A = \{2, 4, 6, 8\}$ and $B = \{6, 8, 10, 12\}$. Find $A \cap B$.

If $X = \{a, b, c, d\}$ and $Y = \{f, b, d, g\},$ find $Y - X$.

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