A-2-m by 1.5-m section of wall of an industrial furnace burning natural gas is not insulated, and the temperature at the outer surface of this section is measured to be 80 C. the temperature of the furnace room is 30 C, and the combined convection and radiation heat transfer coefficient at the surface of the outer furnace is 10 W/m^2*C. it is proposed to insulate this section of the furnace wall with glass wool insulation ( K= 0.038 W/m*C) in order to reduce the heat loss. assuming the outer surface temperature of the metal section still remains at about 80C, plot the thickness of the insulation that needs to be used as a function of the reduction in heat loss.