The DEMAND statement identifies the SAS variable in the ARCDATA=
data set that contains the demand at the node named in the corresponding HEADNODE
list variable. The DEMAND list variable must have numeric values. It is not necessary to have a DEMAND statement if the name
of this SAS variable is _DEMAND_
. See the section Missing S Supply and Missing D Demand Values for cases when the SUPDEM list variable values can have other values. There should be no DEMAND statement if you are solving
an LP.