The unrestricted variable Sj is now the difference between two nonnegative variables 5j and Sf.
We can think of 5i as the number of temps hired and 5; as the number of temps fired. For example, if Sj = 5 and 5t = 0 then 5i
= S - 0 = +S, which represents hiring. If 5i = 0 and
5t = 7 then Sj =0 - 7 = -7, which represents firing. In the first case, the corresponding cost
of hiring is 2005i = 200 X S = $1000 and in the second case the corresponding cost offiring is
4005; =400 X 7 = $2800. Thisidea is the basisfor the development of the objective function.