$\newcommand{\C}{\mathscr{C}}$Let $$ \C := \{ \frac{1}{n} \mid n>0 \} \cup \{0\} \leq \mathbb{R}^2 $$ Be the “convergent sequence space”. Let $S\subseteq C$. We have the following criteria:
Now consider a finite partition $\Pi = \bigcup_{i=0}^n \Pi_i$, where wlog $0\in \Pi_0$. In every case, $\Pi_0$ is closed, since its complement consists of points not containing the $0$.
$\Pi_0$ is finite.
We then know that $\Pi_0$ is not open, since it cannot contain an $\epsilon$-ball around $0$. Let wlog $\Pi_1, \ldots,\Pi_k$ be all the infinite sets. All $\Pi_i$ with $i>k$ must be clopen.
a) There is precisely one infinite set $\Pi_1$.
Since it is cofinite, it is clopen. In our quotient space $\C / \Pi$, We now look for the smallest superset of ${Pi_0} being open: This is already achieved by ${\Pi_0,\Pi_1}$, since the preimage under their
b) There is more than one infinite set.
$Q$: Which of those partitions are $T_0$? $T_1$? $T_2$?