Consider a simple project with two activities - design and implementation. The design activity is scheduled to take 10 days, and the implementation activity is planned for an additional 12 days. Each of these activities will be worked on by different people. Our initial plan is to schedule the design activity right away and work till completion; and the implementation activity is scheduled to begin as soon as design activity is completed. [See the first gantt chart] With this sequential schedule, the project will get completed in 22 days. Moreover, suppose we have to pay each person (both the person working on the design, and the person working on the implementation) $300 per day of work. With the sequential schedule, it will cost us $300 x 22 = $6600. After having learned about concurrent engineering, you decide that maybe it makes sense to partially parallelize these two activities. Suppose you ask the implementation engineer to start working on beginning of day 10 (instead of beginning of day 11 as before), then some of the design specs from the upstream has not have been finalized. [See the second gantt chart]