The key to answering this question with confidence starts with understanding that you are interviewing with Federal Reserve Bank of San Francisco because your interviewer feels that you are a strong candidate for this position. What your interviewer is focusing on with this question is how they could be of most help to you if hired for the job. So, take the time prior to your interview to think about an aspect of the position that would be the most difficult for you to overcome to be up and running at full speed and then take time to explain how you would plan to overcome that hurdle if hired. This structured answer will tell your interviewer that you have put thought to your potential shortcoming with a plan of action.