Asking a professor to change a grade-- GPA issue

<p>This semester i took a philosophy class courses. I have As and A+ in all my assignments but in midterm i took a C. My issues is that i want my GPA average to be above 3.5 and for that i need at least an A- in this class. All my assignments, the midterm and the final exam are graded by the TA. Since the TA is the one who basically decides my final grade, i want to contact her before the grades are posted that i need to get an A- for this course, because i believe that if i ask to change my grade after its is posted, probably it would not happen. The issues is that i want to make sure that i take A- in, although i don't know what is my grade for the final exam. i really don't know how to approach her.
Should i contact her before or after my grade is posted?
Or, should i directly contact the professor? How should i present my issue to her?
If any one has had any experience with a class where although the professor is the one who posts the grades, the TA is the one who decides our final grade, advices are welcomed. This is the first time that i find my self in this situation and i really don't know what to do.

<p>I wouldn't ask to "change" your grade. You earned what you earned. On the other hand, I don't think it's a bad thing to ask if you can redo an assignment that you know you could do better on after meeting with the Professor to discuss what you did wrong. I doubt, however, that you will be able to redo your midterm, but had your "C" been in any other assignment (besides the final) I wouldn't see any harm in asking if you can re-write a paper for a better grade. Unfortunately, you received a "C" on the midterm, which I don't believe should be allowed to be retaken. But if you received "As" on everything else and do well on your final, I honestly can not see the "C" on the midterm bringing you down that much. How much is every assignment worth?</p>

<p>Thanks for the response.
As for the assignment, they are worth 45% of my grade.</p>

<p>Pending a solid grade on your final, I think your overall grade should be fine. Furthermore, your professor may factor in participation points if you are on the edge. Good luck!</p>