A point charge Q moves on the x-axis in the positive direction with a speed of 370 m/s. A point P is on the y-axis at y = +80 mm
. The magnetic field produced at point P, as the charge moves through the origin, is equal to 0.80x10^6 T in the NEGATIVE z direction . When the charge is at x = +40 mm, what is the magnitude of the magnetic field at point P?
