A pin fin of uniform, cross-sectional area is fabricated of an aluminum alloy (k= 160 w/m·k). the fin diameter is d= 4.2 mm, and the fin is exposed to convective conditions characterized by h= 231 w/m2·k. it is reported that the fin efficiency is ηf= 0.65. determine (a) the fin length l and the fin effectiveness ɛf. account for tip convection.