Let $(s_{n})$ be a sequence that converges.
[(a)] Show that if $s_{n} \ge a$ for all but finitely many $n$, then $\lim s_{n} \ge a$.
[(b)] Show that if $s_{n} \le b$ for all but finitely many $n$, then $\lim s_{n} \le b$.
[(c)] Conclude that if all but finitely many $s_{n}$ belong to $[a, b]$, then
$\lim s_{n}$ belongs to $[a,b]$.