If $f(x)=k$ exp, $\{ -(9x^2-12x+13)\}$, is a $p, d, f$ of a normal distribution ($k$, being a constant), the mean and standard deviation of the distribution:
- $\mu = \frac{2}{3}, \sigma = \frac{1}{3 \sqrt{2}}$
- $\mu = 2, \sigma = \frac{1}{\sqrt{2}}$
- $\mu = \frac{1}{3}, \sigma = \frac{1}{3 \sqrt{2}}$
- $\mu = \frac{2}{3}, \sigma = \frac{1}{ \sqrt{3}}$