Heat is lost through a plane wall steadily at a rate

of 800 W. If the inner and outer surface temperatures of the

wall are 20°C and 9°C, respectively, and the environment

temperature is 0°C, the rate of exergy destruction within the

wall is

(a) 0 W (b) 11 W (c) 15 W (d) 29 W (e) 76 W