Solution
= Solution
\b[True.] Let $g=f^{-1}$. For every open $U\subseteq X$,
$$
g^{-1}(U)=f(U),
$$
which is open in $Y$ because $f$ is an <open map>. Thus $g$ is continuous. Together with the given continuity and bijectivity of $f$, this establishes a <homeomorphism>. This is <inverse continuity from an open bijection>.