I cannot yet assign letter grades to this distribution, for we have 2 more homeworks to include and the final exam to include before letter grades will be assigned. However, There are three clear peaks. My thinking now is that IF this was the final grades, I would assign a range of "A" in the highest peak, a range of "B" in the middle peak and range "C" in the lowest peak. I am certain that after the final exam the distribution will look much different.

Normally, one would assign "C" where the average is (about 62), and then use the Standard deviation (Std Dev = 25) to mark off the grades. For example, 62 is a "C". A "C+" is 62+12.5=74.5, and "C-" is 62-12.5=49.9, etc. If the final distirbution is more like a bell curve, I will apply this method.