I bought this material. I was in the rocket class. This kind of material is difficult, but all the students in our class like to buy it (because they are very demanding of themselves). I haven't finished eating since I bought it. The number of questions is too large and difficult. You can buy a difficult classic. It is also good to follow your own situation. Good grades are not good materials, but only a part. As long as it doesn't exceed the standard, it is very important to attend classes.