An 8-m long, unisulated square duct of cross sectional 0.2-m x 0.2-m and relative roughness 10^-8 passes through the attic space of a house. Hot air enters the duct at 1 atm and 80 C at a volume flow rate of 0.15m^3/s. The duct surface is nearly isothermal at 60 C. Determine the rate of heat loss from the duct and the pressure difference between the inlet and outlet sections of the duct.