$3.$ A circular fin with a diameter of $20$ mm and a length of $100$ mm is exposed to a fluid at a temperature of $150\backslash$deg C$.$ The base temperature of the fin is $70\backslash$deg C$,$ and the heat transfer coefficient is $25$ W$/$m$^2$K$.$ The thermal conductivity of the fin is $80$ W$/$mK$.$ Determine the fin efficiency and heat transfer rate from the fin.