Hello. This is Zero. In order to improve your math skills, you should not look at the solution book. The solution is only one of the problem-solving processes, and if you learn it with your eyes before thinking about the process, you will not be able to solve similar problems or application problems. I think the same goes for the problems to think about. The process of creating a working software as code is not like what is in the solution book for math problems. You have to think about the trade-off between abstraction and readability (which have opposite effects), and there are situations where you have to give up transaction serialization to some extent for processing non-standard real-time data. What will help you at this time is not the knowledge you have seen with your eyes, but the experience you have thought about. I did not upload the answers to the problems to think about separately, hoping that you will gain such experience and wisdom. But for those who are still curious, I have set up an online feedback session, so if you are interested, please send me an email. As for using IntelliJ, Since the ability to run and debug WAS (Tomcat) (Enterprise Edition) is available from the Euro version, I decided not to use it when planning the lecture. Also, since I don't need IDE-specific features and I only need to set the classpath, compile, and build without any separate plugins or libraries, I use Eclipse, which is free and allows WAS (Tomcat) control. However, as you suggested, I will create a separate method for setting the backend framework project environment based on IntelliJ and upload it to help you take the course. Thank you for your review.