An experimental arrangement for measuring the thermal conductivity of solid materials involves the use of two long rods that are equivalent in every respect, except that one is fabricated from a standard material of known thermal conductivity while the other is fabricated from the material whose thermal conductivity is desired. Both rods are attached at one end to a heat source of fixed temperature , are exposed to a fluid of temperature T[infinity], and are instrumented with thermocouples to measure the temperature at a fixed distance from the heat source. If the standard material is aluminum, with 200 W/m·K, and measurements reveal values of TA= 75°C and Tb= 55°C at xi for Tb= 100°C and T[infinity]= 25°C, what is the thermal conductivity of the test material?