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: If William drinks water, then Karen is writing a letter. Karen is not writing a letter. If Karen writes a letter, then William is drinking water. Barbara is cooking.
William is not drinking water can be inferred via the modus tollens rule. Karen is not writing a letter and Barbara is cooking can be inferred via the conjunction rule. Barbara is cooking and Karen is not writing a letter can be inferred via the conjunction rule. William is drinking water if and only if Karen is writing a letter can be inferred via the biconditional introduction rule. Karen is writing a letter if and only if William is drinking water can be inferred via the biconditional introduction rule.