There are several ways to go. For one, you can put "Average" in the "Total" row in the Access query design. In query design you can specify menu item "view totals" to toggle that row appearing. Then you can set a query criteria and get the averages, one by one.
You'll probably prefer to use an Access report. If you set up a query that does nothing but output category and rate, you can start a new report, invoking the report wizard, specifying that query as the source; then set the category as a grouping level; then clicking the wizard button "Summary options" and clicking the Sum and Avg buttons - which will produce a report that shows the sum and average after each category.
However, you may or may not intuitively latch on to the design, modification and running of Access reports at your current level. You should really exercise with dummy data and get the hang of it. (Of course, and more importantly, the same holds for the query design.)
If this sounds over your head, it needn't, because all of this is pretty basic; you'll probably spare yourself much frustration with this if you get a "learn Access in 28 days" book, which will probably make you somewhat fluent after the first 6 or 10 chapters (and you may find that most chapters take under an hour). A fuller approach would consider taking the time to work with a broader text such as the MrExcel recommendation atop this forum list.
I don't mean to cop out and say that you can't be helped here unless you "go out and learn Access first." I just suggest you work with at least those two areas - whether with Kamikaze abandon on dummy data, or measured study from a text. That is, if the above concepts seem intimidating.
