Question

How many elements has ?

Answer 1

$$\begin{gathered} \mathrm{Given}:A=\varphi \\ \mathrm{This}\mathrm{means}P\left(A\right)=\left\{\mathrm{\varphi }\right\}. \\ \mathrm{Hence},P\left(A\right)\mathrm{would}\mathrm{have}\mathrm{one}\mathrm{element}. \end{gathered}$$