An insulated container is filled with a mixture of water and ice at `t_c = 0^@C`. Another container is filled with water that is continuously boiling at `t_h = 100^@C`. In a series of experiments, the containers are connected by various thick rods that pass through the walls of the containers (see the diagram). The rod is insulated in such a way that there is no heat loss to surroundings. In experiment 1, a copper rod is used, and the ice melts in `T_1 = 2` min. In experiment 2, a steel rod of the same cross section is used, and the ice melts in `T_2 = 6` min. How long ( in min) would it take to melt the ice if the two rods are used "in series"?