Subject to: ∑i=1mvipxip=1 . ∑j=1sujpyjr−wp−∑i=1mvipxir≤0 ∀ r=1,2,…n. ujp≥ε, vip≥ε ∀ i,j. wp∈ℝ Where ε is a non-Archimedean infinitesimal value for forestalling weights ujp, vip to be zeroed. The formulation stated above refers to the BCC model  which assumes variable returns to scale. Omitting wp in the above formulation the linear program is converted to what is known as CCR model  which assumes constant returns to scale. When the BCC model is applied, the sign of wp that comes out from the solution of the linear program identifies the nature of returns to scale.