b. Have node pairs such as T1, T1' for all twelve targets on
both days. For day 1, Identify the flow on the target arcs be
tj11 and tj21, where j is the target index,
1 refers to the arc with cost -dj and 2 refers
to the arc with cost -0.75dj. Similarly define
tj12 and tj22 for the second day.
Define the binary variables, wj = 1 if target is
hit on the first day and 0 if it is hit on the second day, for
j = 1 to 12.
Add side constraints: tj11 + tj21 ¾ 10wj
and tj12 + tj22 ¾ 10(1 - wj),
for each target j. This forces the flows on a target in day
1 to be 0 unless the target is selected. It forces the flows
on a target in day 2 to be zero unless it is not selected for
This is a mixed integer programming model.