What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Richard were a server, then Richard is an artist. Richard is a server if and only if Sarah is sad. For all x_21, if x_21 were an artist, then x_21 is a server. If Patricia were happy, then Richard is an artist. Sarah is not sad.
If Richard were a server, then Sarah is sad. If Sarah were sad, then Richard is a server. Richard is not a server.