If you want to contest a score on your prelim, do so within one week of the date on which the graded exam was handed back. You must complain to Ke Wang and Jon Ludwig, the grading czars. Please make sure that you've carefully read both the solutions and the notes on grading before you make a complaint.
Prelims submitted for regrading must be accompanied by a written statement that details your concerns.
Concerns about the grading of the final should be addressed directly to Sergei.