A wall is constructed of several layers. The first layer consists of masonry brick 20 cm. thick of thermal conductivity 0.66 W/mK, the second layer consists of 3 cm thick mortar of thermal conductivity 0.6 W/mK, the third layer consists of 8 cm thick lime stone of thermal conductivity 0.58 W/mK and the outer layer consists of 1.2 cm thick plaster of thermal conductivity 0.6 W/mK. The heat transfer coefficient on the interior and exterior of the wall are 5.6 W/m 2K and 11 W/m 2K respectively. Interior room temperature is 22°C and outside air temperature is -5°C.

Calculate:

a) Overall heat transfer coefficient.

b) Overall thermal resistance.

c) The rate of heat transfer.

d) The temperature at the junction between the mortar and the limestone.