3. A proton is released from rest at point A, which is located next to the positive plate of a parallel plate capacitor. The proton then accelerates toward the negative plate, leaving the capacitor at point B through a small hole in the plate. The electric potential of the positive plate is 4.8 kV greater than that of the negative plate. Once outside the capacitor, the proton travels at a constant velocity until it enters a region of constant magnetic field of magnitude 0.25 T. The velocity is perpendicular to the magnetic field, which is directed out of the page. Find the radius r of the circular path on which the proton moves in the magnetic field. if (out of paper) Parallel plate capacitor A-Ombo + +