Which expression gives the magnitude of the magnetic field in the region c < r2 < b (at e?

The electric currents and magnetic materials have an effect called magnetic field. This magnetic field is specified with its direction and magnitude. The magnitude is the strength of the field.

the magnetic field at a distance r from a long straight wire carrying current I can be calculated with the equation:

B = μ I / 2 pi R

where μ is a constant, I is the current and R is the radius.