Moving Charges And Magnetism

Two very long straight parallel wires carry currents \(i\) and \(2 i\) in opposite directions. The distance between the wires is \(r\). At a certain instant of time a point charge \(q\) is at. a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity \(v\) is perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is