I am trying to do a pre-lab assignment for an introductory calc-based E&M course, and it involves the calculation of a magnetic field due to a bar magnet. My first inclination was to use the B = (mu/4pi) * (q (V x R ) / R3) equation, but I am quite certain that this is not the correct approach. There is no single moving charge with velocity V which we can pinpoint, and Identifying every charge is clearly not the intent (integrating could be a possibility, but I am still convinced that there exists some other equation/idea that I can apply). I don't have my book at hand, and we have not discussed anything like this in lecture yet (I do have my note-book). Can someone point me in the right direction?