Pls help

Points A, B, and C are given in the coordinate plane. There exists a point Q and a constant k such that for any point P,

$PA^2 + PB^2 + PC^2 = 3PQ^2 + k$
If $A = (4,-1),B = (-3,1),$  and , $C = (5,-3)$then find the constant k.