How many elements has P(A)

How many elements has P(A), if A = Φ?
Answer
Φ is an empty or null set so it doesn’t have any element.
So number of element n = 0
Number of elements in a power set n[P(A)] = 2ⁿ
plug n = 0 we get n[P(A)] = 2⁰ = 1 used formula [a⁰ =1]
Hence, P(A) has one element.