If A = ϕ then find n{P(A)}.
We have, A = ϕ , i.e. A is a null set.
Then, n(A)= 0
∴ n{P(A)} = 2m , where m = n(A)
⇒ n{P(A)} = 20 = 1.
Thus, P(A) has one element.