If $A$ and $B$ are two sets,then $A \times B = B \times A$ if and only if

If $A=\{2,4\}, B=\{3,4,5\}$,then $(A \cap B) \times (A \cup B) =$

If $A = \{ 2, 4, 5 \}$ and $B = \{ 7, 8, 9 \}$,then $n(A \times B)$ is equal to

If $P = \{a, b, c\}$ and $Q = \{r\}$,find the sets $P \times Q$ and $Q \times P$. Are these two products equal?

Let $A$ and $B$ be two sets such that $n(A)=3$ and $n(B)=2$. If $(x, 1), (y, 2), (z, 1)$ are in $A \times B$,find $A$ and $B$,where $x, y$ and $z$ are distinct elements.

If two sets $A$ and $B$ have $99$ elements in common,then the number of elements common to each of the sets $A \times B$ and $B \times A$ is