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: Susan is playing a game if and only if Charles is a nurse. If it is cold, then Karen is playing squash. Susan is playing a game or it is cold. Charles is a nurse or Karen is not playing squash.
If Karen plays squash, then Charles is a nurse can be inferred via the rewriting rule. If Susan plays a game, then Charles is a nurse can be inferred via the biconditional elimination rule. If Charles were a nurse, then Susan is playing a game can be inferred via the biconditional elimination rule.