In a Mass Spectrometer a Particle of Mass M and Charge

In a mass spectrometer a particle of mass m and charge q is accelerated through a potential difference V and allowed to enter a magnetic field B, where it is deflected in a semi-circular path of radius R. The magnetic field is uniform and oriented perpendicular to the velocity of the particle. Derive an expression for the mass of the particle in terms of B, q, V, and R.

A) qB²R²/V
B) qB²R²/(2V)
C) q²B²R²/V
D) q²B²R²/(2V)
E) qB²R²/(V²)