Problem 3 (30 points) Pure aluminum cylindrical rods are heated to 400C in an oven and then removed from the oven and cooled to 100C through convection with air at 30C with a convection coefficient of 20 W/(m K). The cooling process must be completed in less than 20 minutes. a) Determine the maximum possible diameter of the rods in order to comply with the requirement stated above (15 points) b) For a rod with half the maximum diameter calculated in part a, determine (i) the required time for the cooling process and (ii) the total energy that will be removed from the object, per unit length. during the cooling process (15 points)