50. ••• A circular wire (planar) coil consists of 100 turns and is wound around a very long iron cylinder of radius 2.5 cm and a relative permeability 2200. The loop carries a current of 7.5 A. Find the field strength

(a) at the center of the circular coil and

(b) on the central axis of the iron cylinder 5.0 cm above the center of the coil.