You are managing a project to design microprocessor control systems. The design work was estimated to complete in $3\mathrm{.}5$ months with seven milestones. The sixth milestone is the prototype to be transferred to manufacturing. All milestones before prototyping have been completed ahead of schedule, with the $6$th one being delayed for $4$ months as the protype has been sent back several times due to conflicts between departments. You are now planning to hold a meeting to review the design specifications and handle conflicts between design and manufacturing. Who is at fault?

Group of answer choices

The scheduler

The design engineer

The manufacturer

The project manager