Solution
= Solution
{c}
For <metric spaces>, continuity at $x_0$ means that for every $\epsilon>0$ there is $\delta>0$ such that
$$
\boxed{\operatorname{dist}_X(x,x_0)<\delta
\ \Longrightarrow\
\operatorname{dist}_Y(f(x),f(x_0))<\epsilon.}
$$
The choice of $\delta$ may depend on both $\epsilon$ and $x_0$.