Spend analysis helps to identify savings opportunities that can be quickly and easily attacked, most of the time without significant impact to your company's operations. Making a rough estimate of these savings requires plugging in just a few numbers that you probably have a good handle on already.

So, "let's play sourcing consultant" and get the answer — one that's going to be pretty close to reality given the numbers provided. Just play with the assumptions until they seem right to you. You may be surprised at the result.