Let f: R → R be differentiable at c ε R and f( c )=0. If g (x)=|f(x)|, then at x= c, g is:

Let $\displaystyle f: \mathbf{R} \rightarrow \mathbf{R}$ be differentiable at $\displaystyle \mathrm{c} \boldsymbol{\epsilon} \mathbf{R}$ and $\displaystyle f(\mathrm{c})=0$. If $\displaystyle \mathrm{g}(x)=|f(x)|$, then at $\displaystyle x=\mathrm{c}, \mathrm{g}$ is :