3. (45pts.) A wire with an insulating coating carries a current I and it is bent into the form shown in the gure. The two curved sections are semicircles of radii R1 = R (on the acz plane) and R2 = 313/5 (on the my plane), respectively. The wires are thin enough that the current can run along the artaxis in both directions (left side of gure). 2 RI X (a) Find the magnetic field at the origin. (b) A point charge q crosses the origin with velocity U = (V32 - j). What is the magnetic force on this point charge at this instant of time? (c) Show that the force calculated in part (b) is perpendicular to both the velocity of the particle and the magnetic field