Help Writing A SELECT Query, Please. (Should Be Interesting For You!!!)

All- I would greatly appreciate some assistance in creating a SELECT statement for table headcount in the following problem:

First, find the schema here: http://home.pacbell.net/eulimi/schema_headcount.GIF

The problem:

Given a person_id (a record in the person table), list all headcount records WHERE:
1) headcount.person_id = person.person_id AND
2) the headcount.act_session_id belongs to a activity (from the activity_session table) that the person is allowed to attend by virture of the person's membership in a subexpedition.

Note that:

- A person can be a member of one or more circles (via the circle_person table)
- Each circle belongs to exactly one subexpedition.
- A persons who is a member of a subexpedition (via one or more circles) is entitled to sign up for one or more activities (activity_sessions) associated with the subexpedition.


So, put yet another way, the SELECT command should show, for a given person_id, the list of records in headcount that includes the activities (act_session_id) that the person is entitled to join by virtue of the persons membership in the subexpedition via his circle. (Whew!)

I hope this is enough information. I think the problem would be fun if I knew what I was doing. (SQL newbie here.) I suspect I need several INNER JOINs and a compound WHERE clause.

Thanks in advance!!!