The random variable $X$ follows normal distribution $f(x)=ce\large\frac{-1/2(x-100)^{2}}{25}$ Then the value of $c$ is

Question

$$\begin{array}{1 1}(1)\sqrt{2\pi}&(2)\frac{1}{\sqrt{2\pi}}\\(3)5\sqrt{2\pi}&(4)\frac{1}{5\sqrt{2\pi}}\end{array}$$