N = 400 turns k ■ 40 cm 0.05 cm A = 12 cm² (a) Figure shows a ferromagnetic core whose mean path length is 40cm. There is a small gap of 0.05cm in the structure of the otherwise whole core. The csa of the core is 12cm², the relative permeability of the core is 4000, and the coil of wire on the core has 400 tums. Assume that fringing in the air gap increases the effective csa of the gap by 5%. Given this information, find (a) the total reluctance of the flux path (iron plus air gap) (b) the current required to produce a flux density of 0.5T in the air gap.