A Mass Spectrograph Is Operated with Deuterons, Which Have a Charge

Multiple Choice

A mass spectrograph is operated with deuterons, which have a charge of +e and a mass of
3.34 × 10^-27 kg. Deuterons emerge from the source, which is grounded with negligible velocity. The velocity of the deuterons as they pass through the accelerator grid is 8.0 × 10⁵ m/s. A uniform magnetic field of magnitude B = 0.20 T, directed out of the plane, is present at the right of the grid.
-In the figure,the deuterons are in circular orbit in the magnetic field.The radius of the orbit and the initial sense of deflection are closest to:

A) 60 mm,upward
B) 70 mm,upward
C) 60 mm,downward
D) 70 mm,downward
E) 80 mm,downward