Math review 4. now try your hand on the following order-of-magnitude questions: 1. how many doctors are there in the us? cars does the new york city transit authority own? 2. how many subway 3. how many humans ever lived on the earth? explain your reasoning. note that there are no questions; there are only more plausible and less plausible lines of reasoning. try to make yours as unique "right" answers to these plausible as you can!