One end of a long rod is inserted into a furnace while the other end projects into ambient air. Under steady state the temperature of the rod is measured at two points 75mm apart and found to be 125C X500) and 88.5C respectively while the ambient temperature is 20C. if the rod is 25mm in 278 diameter and heat transfer coefficient for air is 23.36 W/mK, the thermal conductivity of rod material in W/mK is (a) 101.1 (c) 113.2 (b) 115.2 (d) 150