Optical engineering is the most popular major in science and engineering. It's very difficult for you to cross majors and want to pay at public expense. The extra exam is to take two professional courses in the second exam. You haven't passed the first level, so don't think so much for the time being. There will be a remedial class in the school during the professional class, which costs hundreds of dollars to sign up. The public expense ratio is about 1.5. The score line is different every year, roughly 40 points higher than the national line, which is relatively safe. After the initial test, there is basically no big problem in the second test. High marks are the most important.