In the coordinate plane, A=(4,1) B=(6,2) and C=(-1,2) . There exists a point Q and a constant k such that for any point P, PA^2 + PB^2 +

In the coordinate plane, A=(4,1) B=(6,2) and C=(-1,2) . There exists a point Q and a constant k such that for any point P, PA^2 + PB^2 + PC^2 = 3PQ^2 + k. Find the constant k.