Disposable knives and forks are ordered by an environmentally-conscious pizza house. The shape of each (and thus the length, width and profile) are fixed, but the thickness is free: it is chosen to give enough bending-stiffness to cut and impale the pizza without excessive flexure. The pizzeria proprietor wishes to enhance the greenness of his image by minimizing the energy content of his throw-away tableware, which could be moulded from polystyrene (PS) or stamped from aluminium sheet.