1. What would happen to those got 13.5 on midterm? How about an "A"?

Grades will not be determined until the final is taken and all the gradeable homeworks are accounted for (see the syllabus). The only reason I dared to rank students in class is because students feel comfortable doing that.

2. Hopefully you will get us problems more explicitly next time.

This will certainly not happen. There is a basic academic principle that overrides all others - the freedom of creative thought. If I establish a pattern whereby my answers are the only acceptable answers, then we lose that principle. I allow students to argue for more exam points because it encourages them to think more about the questions, not because some students might consider some questions to be ambiguous.