If>=0 isremoved from the definition ofXj' then the variable is assumed unrestricted.The
notation in {} representsthe set ofsubscripts over which a paramor a var is defined.
After defining all the parameters and the variables, we can develop the model itself. The objective function and constraints must each carry a distinct user-defined
name followed by a colon (:). In the Reddy Mikks model the objective is given the
name z: preceded by maximize, as the following AMPL statementstates:
maximize z: sum(j in 1. .n}c[jJ*x(j];