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 y for which y will sleep if and only if y will take a plane. For all y, if y sleeps, then y is fast. For all y, y will not take a plane. For all y, if y were fast, then y is sleeping.
For all y, y will sleep if and only if y is fast can be inferred via the universal biconditional introduction rule. For all y, y is fast if and only if y will sleep can be inferred via the universal biconditional introduction rule. There is at least one y for which if y sleeps, then y is taking a plane can be inferred via the existential biconditional elimination rule. There is at least one y for which if y takes a plane, then y is sleeping can be inferred via the existential biconditional elimination rule. There is at least one y for which y will not sleep can be inferred via the existential biconditional elimination rule.