A material is required for a low cost column with a circular cross section that must support a load FCrit without buckling. If the height of the column is L, derive an expression for the material cost of the column in terms of its dimensions, the price per kg of the material, Cm, and the material density. The cross sectional area, A is a free variable that must satisfy the constraint that the load must not be less than Fcrit. Find three possible candidate materials.