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 Joseph drinks water, then Thomas is a doctor. For all x_9, x_9 is a police officer. Thomas is a doctor if and only if Joseph is a police officer.
If Thomas were a doctor, then Joseph is a police officer can be inferred via the biconditional elimination rule. If Joseph were a police officer, then Thomas is a doctor can be inferred via the biconditional elimination rule.