In Polya's 4 step process of logical mathematical thinking........ the last step is mental

So it turns out it depends on the question, whether or not the last step is mental. I said that with all sincerity the first time.. And turned out, the Prof wanted us to reverse the process and check it out to get the initial numbers. However, in questions requiring doing a list to solve......... the last step is mental. Win for Shelli.