A uniform magnetic field B with magnitude 1.2 mT is directed vertically upward throughout the volume of a laboratory chamber. A proton with kinetic energy 5.3 MeV enters the chamber, moving horizontally from south to north. (Mass of proton is 1.67 × 10⁻²⁷ kg, neglect Earth’s magnetic field). What magnetic deflecting force acts on the proton as it enters the chamber?