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: It is cloudy if and only if Karen is playing squash. Karen is not playing squash. David is playing a game and Michael is a sailor.
David is playing a game can be inferred via the simplification rule. Michael is a sailor can be inferred via the simplification rule. If it is cloudy, then Karen is playing squash can be inferred via the biconditional elimination rule. If Karen plays squash, then it is cloudy can be inferred via the biconditional elimination rule. It is not cloudy can be inferred via the biconditional elimination rule.