Database Question) I'm asking you a question about relational algebra, the middleman.

There is a task of expressing the above questions in relation algebra in the report after taking the class, and I would like to ask if the answer to question a is even if you express the above using the join and natural join twice.

I'd really appreciate it if you could answer me. This is the first liberal arts student to start the restoration, and I actually looked for a lot of clueless things, but I couldn't find the right answer. It may be a basic question, but I'm asking.