Consider two co-axial (i.e. sharing the same axis of symmetry z) circular coils, as shown in the figure below. The radius of coil A is R_A =20 cm while that of coil B is R_B =2 cm. The number of turns is 200 and 1000 for coils A and B respectively. They each carry a current I = 5A but in opposite directions. Find the magnitude of the net magnetic field at the center of coil B. If the current in A is flowing from the front to the back by the top of the coil, what is the direction of this net magnetic field in the figure?