Mid-term1,2,3: basically the exactly same questions are used from the past exams, so if you solved as many questions it would help a lot. Note: the order of questions are different, and they have many questions and its convinations are also different. But they are the same questions thus generally if you solve three sets of past exam questions(40x3=120), you will get a good grade. If you aim at Exemption, then you had better try a bit more, say 5 sets.

Semester Exam: Basically no questions are repeated; the same kind of concepts will be asked, but no exactly same questions. Just 1 or 2 sets of past exam questions are enough, since however many questions you have solved the questions it does not necessarily mean you can get a good grade. Thus you should focus on reviewing the whole area(mid-term1, mid-term2, mid-term3 to refresh your memory.

• 1st semester
1. Mid-Term1: 9
2. Mid-Term2: 9
3. Mid-Term3: 9
4. Semester: 85.6 (<92) -> 4 (not exempted)
you need 92 points for an exemption of oral exam.
• 2nd semester
1. Mid-term1: 8
2. Mid-term2: 9
3. Mid-term3: 9
4. Semester: 103.6 > 92 -> 5.
5. Final: 85.6(1st semester)+103.6(2nd semester)=189.2 -> 5. AND 189.2 > 184 -> exempted!
you need 184 points 1st and 2nd semester combined for an exemption of oral exam. Be careful you can not be exempted if your score at the 1st semester was bad.

The exemption is really helpful. You would see how helpful it is in the exam period. (you would not understand before it comes, because you are busy with classes and mid-terms during the instruction periods and you feel exam-period is far away. But once it comes... You will see.