There are three secretaries who work for four departments. If each of the four departments has one report to be typed out, and the reports are randomly assigned to a secretary, what is the probability that all three secretaries are assigned at least one report?

The answer is 8/9. Could someone walk me through the problem. Note: I don't have the source of the question. Thanks.

See this thread: http://www.manhattangmat.com/forums/tricky-probability-question-t141.html

Note that, due to copyright issues, teachers cannot comment on problems without sources. The source was cited for this problem the first time it was discussed. Just FYI for future.

Also note that 8/9 is not the right answer; I know that's been floating around on some other websites. See the above thread for details.