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_16, x_16 is a janitor if and only if x_16 is a sailor. For all x_16, if x_16 were an electrician, then x_16 is an office clerk. For all x_16, x_16 is a sailor. There is at least one x_16 for which if x_16 were an office clerk, then x_16 is not a janitor.
For all x_16, if x_16 were a janitor, then x_16 is a sailor can be inferred via the universal biconditional elimination rule. For all x_16, if x_16 were a sailor, then x_16 is a janitor can be inferred via the universal biconditional elimination rule.