For purposes of predicting final grades, the standard conversion of percentages to letter grades seems appropriate for this exam. There was a high concentration of scores in the 73-83 range, because many of the midterm questions got either mostly full marks, or mostly few marks. I do expect that cluster of marks to spread out (ie some will stay high, and some will move down). These people should have a better idea where they stand after the second midterm.
The mean score was 75.
The median score was 78.
The following is a "stem and leaf" plot of the raw scores.