Let for any three distinct consecutive terms a, b, c of an A.P, the lines ax+by+c=0 be concurrent at the point P and Q(α,β) be a point such that the system of equations
x+y+z=6,
2x+5y+αz=β and
x+2y+3z=4,
has infinitely many solutions. Then (PQ)2 is equal to____