It could depend on alot of factors - but take a look at
http://www.pjs.com/cms/LinkClick.aspx?fileticket=%2FW6KjXbg%2BIM%3D&tabi...
for a preliminary discussion.

You may find more input under the EB credits at
http://www.leeduser.com/credit/EBOM-2009/IEQp3
and
http://www.leeduser.com/credit/EBOM-2009/IEQc3.3

Hope that helps!