A circumferential fin of rectangular profile is constructed of 1 percent carbon steel and attached to a circular tube maintained at 150ºC. The diameter of the tube is 5 cm, and the length is also 5 cm with a thickness of 2 mm. The surrounding air is maintained at 20ºC and the convection heat-transfer coefficient may be taken as 100 W/m2 · ºC. Calculate the heat lost from the fin.