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 z, if z climbs a mountain, then z is taking a plane. For all z, z will take a plane if and only if z is a sailor. For all z, if z takes a plane, then z is climbing a mountain. For all z, z is not a sailor.
For all z, z will climb a mountain if and only if z will take a plane can be inferred via the universal biconditional introduction rule. For all z, z will take a plane if and only if z will climb a mountain can be inferred via the universal biconditional introduction rule. For all z, if z takes a plane, then z is a sailor can be inferred via the universal biconditional elimination rule. For all z, if z were a sailor, then z is taking a plane can be inferred via the universal biconditional elimination rule. For all z, z will not take a plane can be inferred via the universal biconditional elimination rule.