57. ••• A steel cylinder of radius 5.0 cm and length 4.0 cm is placed in end-to-end thermal contact with a copper cylinder of the same dimensions. The free ends of the two cylinders are maintained at constant temperatures of 95 °C (steel) and 15 °C (copper) and a steady heat flow rate is attained. Under these conditions, how much energy will flow through the cylinders in 20 min?