Two circular coils A and B with their centers lying on the same axis have same number of turns and carry equal currents in the same sense. They are separated by a distance, have different diameters but subtend same angle at a point P lying on their common axis. the coil B lies exactly midway between coil A and the point P. the magnetic field at point P due to coils A and B is $B_1$ and $B_2$ , respectively. then