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 x_15, x_15 is not curious. For all x_15, x_15 is a bartender if and only if x_15 is a sailor. For all x_15, if x_15 were a bartender, then x_15 is curious. There is at least one x_15 for which x_15 is a sailor if and only if x_15 is a bartender.
For all x_15, x_15 is not a bartender can be inferred via the universal modus tollens rule. For all x_15, if x_15 were a bartender, then x_15 is a sailor can be inferred via the universal biconditional elimination rule. There is at least one x_15 for which if x_15 were a sailor, then x_15 is a bartender can be inferred via the existential biconditional elimination rule. For all x_15, if x_15 were a sailor, then x_15 is a bartender can be inferred via the universal biconditional elimination rule. There is at least one x_15 for which if x_15 were a bartender, then x_15 is a sailor can be inferred via the existential biconditional elimination rule.