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 k A while the other is fabricated from the material whose thermal conductivity k B is desired. Both rods are attached at one end to a heat source of fixed temperature Tb, are exposed to a fluid of temperature T8, and are instrumented with thermocouples to measure the temperature at a fixed distance x1 from the heat source. If the standard material is aluminum, with kA = 200 W/m · K, and measurements reveal values of TA = 75°C and TB = 60°C at Xl for Tb = 100°C and Too = 25°C, what is the thermal conductivity kB of the test material?