Finding velocity with magnetism?

[papi]

Homework Statement

An electron moves at right angles to a magnetic field of .14T What is its speed if the force exerted on it is 8.7 X 10^-15 N?

I am at a complete lossfor this question.

 

[hage567]

Look up magnetic force (or Lorentz force law).

 

[papi]

so if F=qvB
then V=Bq/F

but when i plus in the charge for the electron is it negative or positive 1.6 x 10^-19 bc can a velocity be a negative answer?