Two parallel beams of protons and electrons, carrying equal currents are fixed at a separation d. The protons and electrons move in opposite directions. P is a point on a line joining the beams, at a distance x from any one beam. The magnetic field at P is B. If B is plotted against x, which of the following best represents the resulting curve

The magnetic field at points to the right of the proton beam acts perpendicular to the paper inwards (x). The magnetic field at points to the left of the electron beam acts perpendicular to the paper outwards (.).
Magnetic field at mid-point M is zero.
 

Magnetic field at the points closer to proton beam acts perpendicular to the paper inwards (i.e. (x)) and at the points closer to electron beam, it acts outwards (i.e., (.)). In the given options graph (c) satisfies all the conditions