Three point charges are fixed in the xy-plane: a charge \(+2q\) is located at the origin \((0,0)\), a charge \(-q\) is located at \((a,0)\), and a charge \(-q\) is located at \((0,a)\), where \(q > 0\) and \(a > 0\). What is the magnitude of the net electric dipole moment of this system of charges?