Halliday, Resnick & Walker — Temperature, Heat, and the First Law of Thermodynamics: Problem 49

49 In Fig. 18-41a, two identical rectangular rods of metal are welded end to end, with a temperature of $T_1 = 0^\circ\text{C}$ on the left side and a temperature of $T_2 = 100^\circ\text{C}$ on the right side. In $6.0\text{ min}$, $43\text{ J}$ is conducted at a constant rate from the right side to the left side. How much time would be required to conduct $43\text{ J}$ if the rods were welded side to side as in Fig. 18-41b?