Two very long parallel wires in the xy-plane,a distance 2a apart,are parallel to the y-axis and carry equal currents I as shown in the figure.The +z direction points perpendicular to the xy-plane in a right-handed coordinate system.If both currents flow in the +y direction,which one of the graphs shown in the figure below best represents the z component of the net magnetic field,in the xy-plane,as a function of x? (Caution: These graphs are not magnetic field lines.) 
Definitions:
Q1: A fish appears to be 2.00 m
Q9: What is the uncorrected near point of
Q29: An ideal gas is kept in a
Q32: Two identical resistors of resistance R =
Q36: A -3.0-μC point charge and a -9.0-μC
Q37: The 60-Hz ac source of a series
Q45: When monochromatic light illuminates a grating with
Q56: The emf and the internal resistance of
Q58: A very long thin wire produces a
Q75: Under steady state conditions,a piece of wood