Time Period of a Proton in a Magnetic Field

Spent half an hour looking at this problem, but I can't see anyway to get any of the multiple choice answers:

Quote:

Originally Posted by **AQA Specimen Paper**

Protons, each of mass

*m*and charge

*e*, follow a circular path when travelling perpendicular to a magnetic field of uniform flux density

*B*. What is the time period for on complete orbit?

**A** $\displaystyle \frac{2 \pi e B}{m}$**B** $\displaystyle \frac{m}{2 \pi e B}$**C** $\displaystyle \frac{eB}{2 \pi m}$**D** $\displaystyle \frac{2 \pi m}{eB}$

All I know is that it should have something to do with:

$\displaystyle F = m \omega^2 r = m \frac{v^2}{r} = BQv \: , \: \omega = \frac{2 \pi}{T} $

Thanks

Edit: Oh and the answer is **D**