Sorry if this seems like such a simple question, but I'm stumped, and
the Help files are not being terribly helpful--or at least they are
not easy to wade through...

I'm analyzing a set of grades of transfer students. The data I
received is sorted in columns. Column A lists last four (or five)
digits of the student ID numbers, (some of the students appear more
than once because they re-took the course.) Column B lists the
semester each course was taken and Column C gives the grades received.

I have a few things I would like to do with the data:
1. How many unique ID numbers appear in the list.
2. I also would like to count the numbers of A's, B's, etc.

(I used to be able to do this on Cricket Graph, but that's so long
ago...)

Thanks for your help!