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, y is not a lawyer. For all y, if y were a lawyer, then y is playing tennis. There is at least one y for which if y plays tennis, then y is a lawyer.
There is at least one y for which y will not play tennis can be inferred via the existential modus tollens rule. There is at least one y for which y will play tennis if and only if y is a lawyer can be inferred via the existential biconditional introduction rule. There is at least one y for which y is a lawyer if and only if y will play tennis can be inferred via the existential biconditional introduction rule.