It's been several years since I worked on a Norstar Meridian. I have a DR5 software 824 Meridian with 1 expansion. There are three lines; 12 sets (mix 7310 & 7208). The customer wants to access the third line first, then the second, then the first outgoing (and the opposite incoming, of course). How do I set this up? Do I need all three to be in a pool together or is there another way? If in a pool, how do I order it?