Two identical short bar magnets are placed at 120° as shown in the figure. The magnetic moment of each magnet is M. Then the magnetic field at the point P on the angle bisector is given by

(1) $\frac{{\mu }_0}{4\pi }·\frac{M}{d^3}$                (2) $\frac{{\mu }_0}{4\pi }·\frac{2M}{d^3}$               (3) $\frac{{\mu }_0}{4\pi }·\frac{2\sqrt{2}M}{d^3}$             (4) Zero