dr. hoosang hooshmand has a great site that answers questions like this. here is a link to this possible answer to your question. actually i tried to copy and paste but it didn't work. type in
www.rsdrx.com/rsdpuz4.0/puz12.htm or just go to his website by typing in dr. hoosang hooshmand. his answers to questions are called "puzzles". his website is full of very informative material on rsd. unfortunately he is retired now but he was considered one of the top rsd experts in the world.