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: There is at least one x_5 for which if x_5 were a sailor, then x_5 is happy. For all x_5, x_5 is happy if and only if x_5 is a sailor.
For all x_5, if x_5 were happy, then x_5 is a sailor can be inferred via the universal biconditional elimination rule. For all x_5, if x_5 were a sailor, then x_5 is happy can be inferred via the universal biconditional elimination rule.