A thin-walled, uninsulated 0.3m diameter duct is used to route chilled air at 0.05kg/s through the attic of a large commercial building. The attic air is at 370C, and natural circulation provides a convection coefficient of 2W/m^2 K at the outer surface of the duct. If chilled air enters a 15m long duct at 70C, what is the exit temperature and the rate of heat gain? Properties of the chilled air may be evaluated at an assumed average temperature of 300K.