Let A and B be two sets containing four and two elements respectively. Then the number of subsets of the set $A \times B$, each having at least three elements is............

If $A = \{ 1,2,3,4,5,6 \} , B = \{ 1,2 \} ,$ then $\frac { A } { \left( \frac { A } { B } \right) }$ equal to 

If n(A)=115, n(B)=326, n(A-B)=47, then $n(A\cup B)$ is equal to

Examine whether the following statements are true or false:

$\left\{a\right\}\subset \left\{\{a\},\, b \right\}$