A single core cable for66kV three phase system has a conductor of 2 cm diameter and sheathof inside diameter of 5.3 cm. It is required to have twointer-sheaths so that stress varies between the same maximum andminimum values in the three layers of dielectric. Find the positionof inter-sheaths , maximum and minimum stress and b voltages ontheinter-sheaths. Also find the maximum and minimum stress when inter-sheaths are not used.