请让这里懂合同法的人帮我做几个题目,恳请帮忙.谢谢

3. This phrase describes the situation where the parties have a different but reasonable understanding as to the actual product being discussed.

What is ____________________________________.
5. This legal theory or philosophy recognizes that many laws are imposed or accepted not because they seem inherently fair but because the community recognizes that the body imposing the law has the legitimate right to do so.

What is ____________________________________.

13. These rules were developed by judges who, in theory at least, did not create law but merely discovered it in the customs and traditions of the people to whom the rules were to be applied. Later these rules were added to by borrowing legal principles from other sources as well.

What is ____________________________________.
不知道这个要求是否过分,我实在是没有办法.找书也找不到,周围也没有做法律的朋友.非常感谢.