csd, is certainly answering a question that is similar to (and more reasonable than) what was asked, but you aren't answering the exact question. In particular, they ask "how many shoes" not "how many PAIRS of shoes", so you'd presumably have to multiply your answer by 2. Additionally, they ask how many CAN be sold, not how many will likely be sold. So, to be "detail-oriented" you'd instead want to try and estimate, not how many people will buy, but how many could possible be sold in the US. In which case, you need to consider the cost of the materials/labor, the amount of the materials/labor available, the rate at which shoes can be made, and the total amount of payment that people in the US could pay. To make it statistical, throw in some distributional assumptions and error estimates, and you'll have an answer for them, give or take some amount. But, that is really pedantic... So, if you answer with this, they might just ask you to leave.