An oven wall has a composite wall consists of 3 different materials. The thermal conductivity of inner layer ( material A ) and the outer layer ( material C ) are 35 W/mK and 40 W/mK. The thickness for both layer materials are 300mm and 150mm. layer ( material B ) is constructed between layer A and C with its thickness is 200mm. The temperature for outer surface and inner surface of the oven are 40C and 550C,while the temperature inside the oven is 700C. The heat transfer coefficient in the oven is 25W/m^2K. Calculate rate of heat transfer per m^2 area.