To reach your figure, you'll need to decide on how that dollar amount might be relevant to some action or decision someone (such as yourself) will take. You'll need to make specific assumptions about why the dollar amount is relevant and (consequently) what is relevant in the calculation of that dollar amount. All of these assumptions should be clearly identified, and, if possible, justified.
For any calculations you do, it's best if you can use actual data, but it's also acceptable to estimate data. Your approach, however, should be internally consistent; you should not add apples and oranges unless you are counting pieces of fruit. If you choose to add a bunch of numbers, please use a table.
You'll be assessed both on your ability to be precise and thoughtful, and equally importantly, original and persuasive. This paper will contribute 12.5% toward your final grade.