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 z, if z drinks water, then z is a taxi driver. Robert is not drinking water. For all z, if z were a taxi driver, then z is drinking water. Susan is a server.
Robert is not drinking water and Susan is a server can be inferred via the conjunction rule. Susan is a server and Robert is not drinking water can be inferred via the conjunction rule. For all z, z will drink water if and only if z is a taxi driver can be inferred via the universal biconditional introduction rule. For all z, z is a taxi driver if and only if z will drink water can be inferred via the universal biconditional introduction rule.