Question

Consider the determination of the momentum of a high energy charged particle by its deflection in the field B of a solid iron magnet. Assuming that there is no scattering and the momentum doesn't change, show that in traversing a distance s, the deflection is expressed by\[\phi_{rms}=\frac{ s }{ \rho }=\frac{ Bes }{ pc }=\frac{ 300Bs }{ pc }\]where rho is the radius of curvature. I don't understand the 300 bit.