$1.$ A fin is attached to a $20$ cm diameter circular pipe that carries hot water at a temperature of $80\backslash$deg C$.$ The fin is made of aluminum and has a length of $30$ cm and a thickness of $2$ mm$.$ The convective heat transfer coefficient between the fin and the surrounding air is $25$ W$/$m$^2$K$.$ Determine the rate of heat transfer from the fin to the surroundings.