Problem 1: A rectangular beam of cross section panel has a fixed width, b, and length, L. The thickness is h. The moment of inertia for calculating the bending stress is I = bh/12. The maximum bending moment applied to the beam is Mmax. If the beam stress cannot exceed the yield stress (y), derive the material index to help us choose the lightest weight beam material. b Problem 2: A beam has a rectangular cross-section with the width b always being 3 times the height, h. For the same conditions as Problem 1, find the material index that helps us choose the minimum weight beam.