Question

How many elements has P(A), if A = Φ?

Answer 1

We know that if A is a set with m elements i.e., n(A) = m, then n[P(A)] = 2^m.
If A = Φ, then n(A) = 0.
∴ n[P(A)] = 2⁰ = 1
Hence, P(A) has one element.