Assume that the length L {\displaystyle L} and tension P {\displaystyle P} are fixed, making them design variables. Lastly the cross sectional area A {\displaystyle A} is a free variable. The objective in this situation is to minimize the weight w {\displaystyle w} by choosing a material with the best combination of material variables ρ , σ {\displaystyle \rho ,\sigma } .