8月12日（月・祝日）に、自分（大人）と高校生の息子、小学生 of 娘の3人でプールに行きます。料金は全部でいくらかかりますか。
💡 Detailed Explanation
The correct choice is Option 3: '1000 yen.' Let's calculate based on the rules: 1) Opening Check: The pool is closed on Mondays ('毎週月曜日'), BUT with an exception: '月曜日が祝日の場合は開いていて、次の日の火曜日が休みになります' (If Monday is a holiday, it is open, and the following Tuesday will be closed). Since August 12 is a Monday AND a holiday ('月・祝日'), the pool is OPEN. 2) Rate Calculation: '自分' (Adult): 400 yen. '高校生の息子': categorized under '大人（高校生以上）' (Adult [High school students and above]): 400 yen. '小学生の娘': categorized under '子ども（小・中学生）' (Child [Elementary/Junior high students]): 200 yen. Total: 400 + 400 + 200 = 1000 yen.