Thanks a lot for your answers! Yes, it makes sense that everyone should not be writing on the same pairings, of course.

2. Yes, I meant could two people work (separately but at the same time) on the same prompt.

So, if I understand correctly, first I choose a rare pairing that is not claimed, then I choose or mix a set of prompts, and then... what do I do with the prompts? Write a story with all of them in it or one story for each prompt? Or can I just use six of the prompts and ignore the rest?