Bhut hard !!!!!!!!!!! xD

Set :- A collection of well defined objects. A set may have infinite or finite objects .Every object is called element of the set.

Subset :- It is the set of few or all elements of a set.

Power set :- It is the set of all subsets of the set including itself and the empty set.

=======================================

Power set is the set of all possible sets.

D = { p, q, r, s }

P ( D) = { p, q, r, s, ( p, q) , ( q, r) , ( r, s) , ( s, p) , ( p , r) , ( q, s) , ( p, q, r) , ( q, r, s) , ( p, r, s) , ( p, q, s) , ( p, q, r, s), Ø }

The number of elements in set n ( D) = 4

Number of elements in power set n (P ( D))

Therefore, Number of elements in power set = 2^4 = 16 .