A bar of copper of length 75cm and a bar of length 125cm are joined end to end. Both are of circular cross – section with diameters 2cm. The free ends of copper and steel are maintained at `100^oc and 0^oc` respectively. The surfaces of the bars are thermally insulated. What is the temperature of copper – steel junction? Thermal conductivity of copper `= 9.2xx10^(-2)k cal |m|'^oc|s` and that of steel is `1.1xx10^(-2) k