The process of heating steel and then cooling it to make it less brittle is called annealing. During the heating stage, a 100mm-thick steel plate, initially at a temperature of 200oC, is to be heated to a minimum temperature of 550oC using a gas furnace that heats both sides of the plate where the gas is at 800oC and the heat transfer coefficient is 250 W/m2.K. Assume that the thermal conductivity, density, and heat capacity of the plate are 48 W/m.K, 7830 kg/m3, and 550 J/kg.K, respectively. How long should the plate be left in the furnace?