How To Find The Mass Of A Particle In A Spectrometer In Which Two Particles Having The Same Charge And Velocity

Question

The figure shows a rudimentary mass spectrometer based on charged particles entering a region with a velocity that is perpendicular to a uniform magnetic field that permeates the region (the gray dots represent a uniform magnetic field pointing out of the page). Assume that two particles having the same charge enter the B-field region with the same velocity. I r2 = 2r1 then m2 (the mass of particle 2), is: