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: William is sad. David is drinking water if and only if Thomas is playing squash. Karen is not playing tennis. Karen is playing tennis if and only if Thomas is playing squash.
William is sad and Karen is not playing tennis can be inferred via the conjunction rule. Karen is not playing tennis and William is sad can be inferred via the conjunction rule. If David drinks water, then Thomas is playing squash can be inferred via the biconditional elimination rule. If Karen plays tennis, then Thomas is playing squash can be inferred via the biconditional elimination rule. If Thomas plays squash, then David is drinking water can be inferred via the biconditional elimination rule. If Thomas plays squash, then Karen is playing tennis can be inferred via the biconditional elimination rule. Thomas is not playing squash can be inferred via the biconditional elimination rule.