12. (GBR 4) $)^{\mathrm{MmO1}}$ Find all functions $f$ defined on the positive real numbers and taking positive real values that satisfy the following conditions:
(i) $f(x f(y))=y f(x)$ for all positive real $x, y$.
(ii) $f(x) \rightarrow 0$ as $x \rightarrow+\infty$.