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_7, if x_7 sleeps, then x_7 is a sailor. For all x_7, if x_7 were a taxi driver, then x_7 is sleeping. For all x_7, x_7 is a sailor if and only if x_7 is poor.
For all x_7, if x_7 were a taxi driver, then x_7 is a sailor can be inferred via the universal transitivity rule. For all x_7, if x_7 were a sailor, then x_7 is poor can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were poor, then x_7 is a sailor can be inferred via the universal biconditional elimination rule.