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 takes a plane, then z is playing a game. For all z, z will not make tea. For all z, z will play a game if and only if z will make tea. There is at least one z for which if z plays a game, then z is taking a plane.
There is at least one z for which z will play a game if and only if z will take a plane can be inferred via the existential biconditional introduction rule. There is at least one z for which z will take a plane if and only if z will play a game can be inferred via the existential biconditional introduction rule. For all z, if z plays a game, then z is making tea can be inferred via the universal biconditional elimination rule. For all z, if z makes tea, then z is playing a game can be inferred via the universal biconditional elimination rule. For all z, z will not play a game can be inferred via the universal biconditional elimination rule.