Carbonsteel (AISI 1010) shafts of 0.1-m diameter are heat treated in a gas-fired furnace whose gases are at 1200K and provide a convection coefficient of 100W/m2K. If the shafts enter the furnace at 230K, use the lumped capacitance model to estimate how long must they remain in the furnace to achieve a centerline temperature of 800K? Use =7832kg/m3,k=51.2W/(mK),c=541 J/(kgK) and =1.21105m2/5. They must remain in the furnace for