In House or Outsource?

Pretend you are again a manager of your favorite manufacturing company. You have been asked to determine whether a product (one of your choosing) should be manufactured in-house or outsourced to another vendor. Discuss the relevant costs you would consider for this decision as well as irrelevant costs and sunk costs. How would you use differential analysis to arrive at this decision? Are there any other items that should be considered when making this decision?