So, I agreed to help a local business with a dinner party. Party of 20, prime rib. 

When I get to the kitchen, they have a small, organic strip loin. I expressed that the strip loin wouldn't be enough to serve 20, and was sent to the store. Picked up a half of a prime there.

Back at the kitchen, I throw both the prime and the loin in the oven. The prime rib turned out exactly as planned, the loin was overdone and dry.

AITA for not making the best out of the product I was given, or should they have supplied the proper cut of meat? 

Thanks! 