BCS Exam FBA15 Topic 2 Question 6 Discussion

An IT department needs to upgrade its hardware to run the new version of an established operating system. The cost of this required upgrade is $2 million. As an alternative, the IT director has suggested that the company should change to a completely different operating system. Although this will cost $6 million, the change will bring many other benefits, including cheaper maintenance costs and increased security. What is the avoided cost in his proposal?