A point charge moving in a magnetic field of 1.24 Tesla experiences a force of 0.813·10-11 N. The velocity of the charge is perpendicular to the magnetic field. In this problem, we use the points of the compass and `into' and `out of' to indicate directions with respect to the page. If the magnetic field points west and the force points out of the page, then select True or False for the charge Q.

so I soleved all the question expect of the last one

--The speed of the charge is 0.410·108 m/s. Calculate the magnitude of the charge.
1.60×10^-19 C
-- The path of the charge in the magnetic field is a circle. Assume that the charge is positive and has a mass of 1.673·10-27 kg, the mass of a proton. What is the radius of the circle?
3.46×10^-1 m
-- What is the orbital frequency of the charge in the previous problem?
how I can do it,? I tried f=qB/2*pi*m.. I got.. 1.88*10^45 Hz ! But it's wrong!

You could find the periodic time first, then get the inverse.