1. A long rectangular geometry with a length of L and a diameter of D is mounted onto a wall kept at a temperature of T0. The L/D ratio of the fin is reasonably higher than unity. The heat is transferred from the fin to the enviroment at a temperature of T3. The convective heat transfer coefficient on the fin surface and the heat conductivity of the fin are h and k, respectively. a) Establish the e ergy balance with appropriate assumptions (20 points). b) Write the boundary conditions (10 points)