For paperboard composed of 2 layers of the same thickness, answer the questions below. Top Layer: d, E Bottom Layer:d, E T a.) Derive a relation between the bending stiffness, Sb, the total thickness of the sheet, d, and the 2 moduli, E1 and E2. b.) If E2 is twice the magnitude of E1, calculate the % increase in bending stiffness, Sb, for a sheet composed of the 2 layers versus a sheet of equal thickness with a constant in- plane modulus, E, throughout.