(a) Verify whether the function f defined by $f(x) = \begin{cases} x \sin\left$ \frac{1}{x} \right$, & x \neq 0 \\ 0, & x = 0 \end{cases}$ is continuous at $x = 0$ or not. OR (b) Check for differentiability of the function f defined by $f(x) = |x - 5|$, at the point $x = 5$.