The concrete wall of a building is 0.10 m thick. The temperature inside the building is 20.0C, while the temperature outside is 0.0C. Heat is conducted through the wall. When the building is unheated, the inside temperature falls to 0.0C, and heat conduction ceases. However, the wall does emit radiant energy emitted per seond per square meter due to conduction. Wha tis the emissivity of the wall.