Let $f : \mathbb{R} \rightarrow \mathbb{R}$ denote the function defined by $f(x)= (1-x^{2})^{\frac{3}{2}}$ if $|x| < 1$, and $f(x)=0$ if $|x| \geq 1$. Which of the following statements is correct ?
- $f$ is not continuous
- $f$ is continuous but not differentiable
- $f$ is differentiable but $f'$ is not continuous.
- $f$ is differentiable and $f'$ is continuous.