If $A$ and $B$ are any two non empty sets and $A$ is proper subset of $B$. If $n(A) = 4$, then minimum possible value of $n(A \Delta B)$ is (where $\Delta$ denotes symmetric difference of set $A$ and set $B$)

State whether each of the following set is finite or infinite :

The set of circles passing through the origin $(0,0)$

State which of the following sets are finite or infinite :

$\{ x:x \in N$ and $x$ is odd $\} $

State whether each of the following set is finite or infinite :

The set of lines which are parallel to the $x\,-$ axis

Which of the following are sets ? Justify your answer.

The collection of all even integers.

Match each of the set on the left described in the roster form with the same set on the right described in the set-builder form:

$(i)$  $\{ P,R,I,N,C,A,L\} $	$(a)$  $\{ x:x$ is a positive integer and is adivisor of $18\} $
$(ii)$  $\{ \,0\,\} $	$(b)$  $\{ x:x$ is an integer and ${x^2} - 9 = 0\} $
$(iii)$  $\{ 1,2,3,6,9,18\} $	$(c)$  $\{ x:x$ is an integer and $x + 1 = 1\} $
$(iv)$  $\{ 3, - 3\} $	$(d)$  $\{ x:x$ is aletter of the word $PRINCIPAL\} $