An electrical wire with a diameter of 1.6 mm is insulated by rubber with a thickness of 2.2 mm and k = 0.27 W/(m K). The air surrounding the insulated wire has a temperature of 25 C and h = 53 W/(mK). The temperature of the rubber cannot exceed 80 C. (a) What is the maximum allowable electrical power that may be dissipated per unit length of the wire? (b) What is the critical radius of the insulation layer?