A steel bar [p = 7800 kg/m\\\', c- 0.5 kJ/(kg "C), and i 50 W/(m "C)) of diameter D - 5 cm is to be annealed by slowly cooling from T-800°C to 120°C in an ambient at T 50°C. If the heat transfer coefficient between the ambient air and the surface of the bar is h- 45 W(m. "C), determine the time required for the annealing process by applying the lumped system analysis,