4. (12 pts) An infinite long fin with rectangular cross section is exposed to the ambient air with T-40 "C and

the heat transfer coefficient of 10 W/(m2K). The fin is fabricated from stainless steel with a thermal

conductivity of 17 W/(m K). The fin length, width, and thickness are 90 cm, 5 cm and 0.3 cm.

respectively. The fin base temperature 7,280 °C. Determine the heat lost by the fin (unit in W).

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