(a) :Copper wire windings on the iron ring forms a toroid.Magnetic field due to a toroid is given by B = \\mu n I where \\mu is the permeability of the medium, n is the number of turns per unit length and I is the current flowing.Also, \\mu = \\mu_r \\mu_o \\implies \\ B = \\mu_r\\mu_o nI (b) : Susceptibility of the magnetic material is given as \\chi = 0.9853 Since the magnetic susceptibility of paramagnetic material is positive. So the given substance must be a paramagnetic material.