Consider a project with seven tasks. Three tasks tasks 3, 4, and 5 require a specific resource for completion; all needed resources must be available at the site before a task can be started.

Task	Duration	Predecessor (s)	Units of Resource Needed	Value of Completed Task
1	3	-	-	-
2	2	1	-	-
3	3	1	10	$4000
4	3	1	10	$3000
5	3	3	12	$5000
6	1	4	-	-
7	1	2, 5,6	-	-

Each resource unit cost $100; no quantity discounts are available. In addition, it costs $2 per unit per time period to hold this resource in stock, and it costs $45 just to place an order for materials (independent of the number of units ordered). When should each task in the project be started and when and how many resources should be ordered to minimize total project costs?