Formulate the following problem with the help of conditional constraints. A lumber operation wishes to build temporary roads from Forests 1 and 2 to Sawmills A and B.
Due to topography and environmental regulations, roads can be built only in certain combinations:
(a) from 1 to A, 1 to B, and 2 to B;
(b) from 1 to A, 1 to B, and 2 to A;
(c) from 1 to A, 2 to A, and 2 to B.
Each sawmill j requires dj units of timber, the unit cost of shipping timber over a road from forest i to sawmill j is cij , and the fixed cost of a road from i to j is fij .
Choose which roads to build, and how much timber to transport over each road, so as to minimize cost while meeting the sawmill demands. Now, formulate the problem without conditional constraints and with a disjunctive linear constraint.