The following are estimate letter grades based on the cummulative scores that 
you recived so far (25% Midterm I + 25% MidTerm II + 20% HW = 70%)

Score   Letter	#Students 
[55,70]   A	   12
[48,55)   B+       22	
[40,48)   B        32
[35,40)   C+        7
[30,35)   C         3
[25,30)   D         3

These numbers are just approximations and letter grades are merely estimations, 
and NOT binding. Your final letter grade still very much depends 
on how well you and the class do on the final exam.

For example, if your cumulative score is currently 52 you are likely 
to get a B+ (with a slightly above average performance in the final exam).  
However, you can stil get an A, by achieving one of the top scores 
in the final exam. On the other hand, your letter score could drop 
to B (or even C+) if your final exam performance turns out to be (very) poor.