Finding the zero of a derivative

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I have a question on finding the zero of a function $h(a)$ which:

$$2aE(\bar{X}^2) - 2*\mu*E(\bar{X}),$$ where $\bar{X}$ follows a normal distribution $\left(\mu, \dfrac{\sigma^2}{n}\right)$

My work so far:

$$2aE(\bar{X}^2) = 2\mu E(\bar{X})$$
$$\to \dfrac{a}{\mu} = \dfrac{E(\bar{X})}{E(\bar{X}^2)}.$$

I dont know what go from here.