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_6, x_6 will take a plane if and only if x_6 will make tea. For all x_6, if x_6 sleeps, then x_6 is making tea. There is at least one x_6 for which x_6 will not take a plane. For all x_6, if x_6 takes a plane, then x_6 is sleeping.
For all x_6, if x_6 takes a plane, then x_6 is making tea can be inferred via the universal transitivity rule. For all x_6, if x_6 takes a plane, then x_6 is making tea can be inferred via the universal biconditional elimination rule. For all x_6, if x_6 makes tea, then x_6 is taking a plane can be inferred via the universal biconditional elimination rule. There is at least one x_6 for which x_6 will not make tea can be inferred via the existential biconditional elimination rule.