4. (15 points) Consider a wall made up of 5 layers of 0.5-mm-thick wood (k= 0.11 W/m K) with with 2-mm-thick air space (k = 0.026 W/m K) between the layers. Assuming the inner surface temperature of the wall to be 25C and the surface area to be 2 m?, a) determine the rate of heat loss through the wall when the temperature of the outdoors is 0C and the heat transfer coefficient at the outer surface is 30 W/m²K. b) Determine the rate of heat transfer if the wall is made of 1-mm-thick wood(neglect air resistance)? c)What should be the thickness of a glass insulation (k=0.035 W/m-K) if the same level of thermal comfort were to be achieved by replacing the wood with glass insulation?