P4. The inner and outer surfaces of a 12 mm-thick 1-m x 1-m window glass in winter are 20 C and 2 C, respectively. If the thermal conductivity of the glass is 0.82 W/m . C, determine the amount of heat loss, in kJ, that occurs through the glass over a period of 8 h. What would your answer be if the glass were half as thick