The gasoline engine

The gasoline engine on a hay bailer has rectangular fins for cooling. The outer part of the engine is kept at 140 F = 60 C, while the surrounding air has T = 20 C. The fins are thin, are made of ordinary 1.5% carbon steel, have a thickness t = 1/16” = 1.59 mm, a width of w = 1.0 cm, and a length L = 4.0 cm. The fins operate in an environment that gives a heat transfer coefficient of h = 18.7 W/m2-K. How many fins are required to remove 5.0 hp = 3.68 kW of waste heat? Also calculate the efficiency of the fins. Number of fins = __________? Efficiency = _________?