If $f(x)$ is a p.d.f of a normal variate $x$ and $X\sim N(\mu,\sigma^{2})$ then $\int\limits_{-\infty}^{\mu}f(x)dx$ is

Question

$$\begin{array}{1 1}(1)undefined&(2)1\\(3).5&(4)-.5\end{array}$$