Let for any three distinct consecutive terms $a, b, c$ of an A.P, the lines $a x+b y+c=0$ be concurrent at the point P and $\mathrm{Q}(\alpha, \beta)$ be a point such that the system of equations $$ x+y+z=6 $$ $2 x+5 y+\alpha z=\beta$ and $x+2 y+3 z=4$, has infinitely many solutions. Then $(\mathrm{PQ})^2$ is equal to