Let $x_1, x_2, \ldots, x_{10}$ be ten observations such that $\sum_{i=1}^{10}(x_i - 2) = 30$, $\sum_{i=1}^{10}(x_i - \beta)^2 = 98$, $\beta > 2$, and their variance is $\dfrac{4}{5}$. If $\mu$ and $\sigma^2$ are respectively the mean and the variance of the observations $2(x_1 - 1) + 4\beta,\, 2(x_2 - 1) + 4\beta,\, \ldots,\, 2(x_{10} - 1) + 4\beta$, then $\dfrac{\beta \mu}{\sigma^2}$ is equal to