 Equivalently, the value of the objective function is decreased if the pivot column is selected so that the corresponding entry in the objective row of the tableau is positive.If there is more than one column so that the entry in the objective row is positive then the choice of which one to add to the set of basic variables is somewhat arbitrary and several "entering variable choice rules" such as Devex algorithm have been developed.If all the entries in the objective row are less than or equal to 0 then no choice of entering variable can be made and the solution is in fact optimal.