a long wire with current I is bifurcated as shown in the figure dividing curent equally.The magnetic feild at point (0,a) is :

Dear student 

Let us assume that the point is P(0,a)

The magnetic field due to given loop at point P is due to vector sum of magnetic field produced due to loop ABCD and ABEF assume ABCD as y plane , ABEF as x plane.
]Magnetic filed due to loop ABCD is along j direction and magnetic field due to ABEF is along i direction. Magnitude due to these both loops are equal so the total magnetic field at point P will be
0.707(j+i)