One proton gains kinetic energy from a resting state through an electric potential of 1.0 kV and enters a uniform magnetic field with an intensity of 0.040 T. At this time, what is the radius of the proton's orbit in cm? (mass of proton mproton = 1.67 × 10-27 kg, charge of proton e = 1.60 × 10-19 C)