A positively-charged particle having mass 7.20 x 10^-8 kg is travelling due east having a speed of 85.0 m/s and enters a 0.310 T uniform magnetic field. The particle moves via one-quarter of a circle in a time of 2.20 x 10^-3 s, at which time it leaves the field heading due south. All throughout the motion the particle moves perpendicular to the magnetic field.
i) Determine the magnitude of the magnetic force on the particle?
ii) Determine the charge on the particle?