public void addMeetingNotes(int id, String text) throws IllegalArgumentException, IllegalStateException, NullPointerException {
		if (text == null) {
			throw new NullPointerException("You cannot add a null text string to a meeting.");
		}
		if (!suppliedMeetingExists(id)) {
			throw new IllegalArgumentException("The meeting ID you supplied does not exist.");
		}
		Meeting m = getMeeting(id);
		Calendar mDate = m.getDate();
		if (dateIsTodayOrFutureDate(mDate)) {
			throw new IllegalStateException("You cannot add notes to a future meeting.");
		} else {
			PastMeeting pm = (PastMeeting) m;
			pm.addNotes(text);
		}
	}