A glass window pane is 1.2 m wide, 1.5 m wide and 3 mm thick. The temperature at the inner surface of the glass is 22o C and at the outer surface 4oC. How much heat is lost each hour through the window? The density of glass is 2300 kg/m3, the specific heat is 840 J/kgC, the coefficient of linear expansion is 8.5 x 10-6 1/C and thermal conductivity is 0.80 J/smC.