Buy a lb per person for that meal. Leftover is GREAT food!
Think ahead about how the people like the Prime Rib cooked. If you all like it like you get in town, remember that both ends will be cooked much more. So, you would need to buy at least enough to cut them off, and still have enough servings left. The ends are not wasted, as good as leftovers. But, they will NOT be pink in the center!
If all want pink centers, buy two lbs more than the number of guests.
Put rub on the outside. Let set for a couple hours after, and get the meat to room temp. Put in a 400Deg oven for 30 minutes, then drop temp to 350.
Cook until center is 126 deg. Remove from oven, tent with aluminum foil tightly, and let set for 30-45 minutes. Remove foil for a few minutes, it will still be hot. Serve.
Yum Yum!
We do whole ribs, takes about two hours. However, with partial cuts, will take a little less time.