Diagram: http://www.webassign.net/mi3/19-073-PROB3roundwithcompass.jpg The figure is a top view of a circuit containing three identical light bulbs (the rest of the circuit including the batteries is not shown). The direction of the North pole is toward the right. The connecting wires are made of copper. (d) There are 6.3 e28 mobile electrons per cubic meter in tungsten. The cross-sectional area of the tungsten filament in bulb B1 is 0.01 mm2 (1 mm2 = 1e-6 m2). The electron mobility in hot tungsten is 1.2e-4 (m/s)/(N/C). Calculate the magnitude of the electric field inside the tungsten filament in bulb B1.