Step 3: Identify the Constraints
Demand Constraints ( )
Words: Total steel available in month 1 should be at least the demand.
Decompose:
Mathematics:
Advantage of Grouping: Letting Di be the demand in month i, other
constraints in the group have the same form:
Total steel available in month 1
= amount in inventory at the beginning of month 1
+ amount produced in month 1.
Ii - 1 + xi ≥ Di
(i = 1, 2, 3, 4)