(a) Four long straight parallel wires pass through the x-y plane at a distance of 4.0 cm from the origin. The figure shows the location of each wire, and its current. Find the net magnetic field at the origin because of these wires. (b) 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 RA =20 cm while that of coil B is RB =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? A(200 turns) B(1000 turns) OI = 30 A 20 cm 2 cm Common axis O 14 = 20 A 12 = 20 A 13 = 10 A