The current density inside a long, solid, cylindrical wire of radius a is in the direction of the central axis, and its magnitude varies with radial distance r from the axis according to J = br^2, where b is a positive constant. NOTE: Express your answers in terms of the given variables and μ₀.
(a) Determine the magnitude of the magnetic field as a function of distance r for 0 ≤ r ≤ a.
(b) Determine the magnitude of the magnetic field as a function of distance r for r ≥ a.