Emergency Vehicle Positioning, Inc. (EVPI), has developed a satellite-based tracking system that continuously updates and displays the location of every vehicle in its network. A recently signed contract presents new technical challenges that may make the normally installed system inadequate. While it is possible to augment the system so that it will definitely work, doing so would entail considerable cost. This case is a modified version of "Integrated Siting Systems, Inc." (UVA-QA-0441). The only difference is that the QA-0441 provides all possible conditional probabilities, offering a slightly different introduction to Bayes's Theorem. In this case, only the recent conditional probabilities are provided. Indeed, except for the name, date, final paragraph (which mentions the other probabilities), and the exhibit on conditional probabilities, the cases are identical. Therefore, the teaching note for the Integrated Siting Systems case (UVA-QA-0441TN) is also appropriate for this case.