What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all x, x is a nurse if and only if x will cook. Charles is cooking or Richard is a writer. Charles is a nurse or Richard is not a writer.
If Richard were a writer, then Charles is a nurse can be inferred via the rewriting rule. For all x, if x were a nurse, then x is cooking can be inferred via the universal biconditional elimination rule. For all x, if x cooks, then x is a nurse can be inferred via the universal biconditional elimination rule.