Consider a line L passing through the points P (1,2,1) and Q (2,1,-1). If the mirror image of the point A (2,2,2) in the line L is (α, β, γ), then…

Consider a line L passing through the points $\displaystyle \mathrm{P}(1,2,1)$ and $\displaystyle \mathrm{Q}(2,1,-1)$. If the mirror image of the point $\displaystyle \mathrm{A}(2,2,2)$ in the line L is $\displaystyle (\alpha, \beta, \gamma)$, then $\displaystyle \alpha+\beta+6 \gamma$ is equal to $\displaystyle \_\_\_\_$.