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 y, if y were a nurse, then y is playing squash. There is at least one y for which y will play squash if and only if y will take a plane. For all y, if y takes a plane, then y is a nurse.
For all y, if y takes a plane, then y is playing squash can be inferred via the universal transitivity rule. There is at least one y for which if y plays squash, 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 playing squash can be inferred via the existential biconditional elimination rule.