Finding the mass of an atom - bainbridge mass spectrometer question

[rugapark]

Q. In a particular spectrometer, doubly ionised $$\stackrel{12}{6}$$C and singly ionised $$\stackrel{6}{3}$$Li atoms are detected. The ratio of the path radii is 1.00252, the Li having the larger value. The fields are constant. Find the mass of of the lithium atom.

I can only think of the equation which links electric force and circular motion in order to find the mass of the atom, however I can't seem to draw out the info needed to use the equation:

m = q $$\frac{BR}{v}$$

where q is the charge, B is the magnetic field, and v is the velocity of the atom.

 

[mgb_phys]

It's just a ratio thing.
What do you know about the mass of a Carbon12 atom (hint think standards)