These are very similar to the 'Tell me about' type of questions. They want a specific example from your work experience. But if the position is an engineer position, you will not get questions about revenue and cost, but you might get one about efficiency. In other questions, I gave an example of reducing cost, so I will use this time to give an example of increasing revenue.
All examples will be different because everyone has different experiences. When you think of your own, you should primarily be concerned about how clear you are. Think of something you did and put them into words. Having answers ahead of time will keep you organized during the interview.