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 will make tea if and only if y will play tennis. There is at least one y for which y will play tennis or y will not make tea.
There is at least one y for which if y makes tea, then y is playing tennis can be inferred via the existential rewriting rule. For all y, if y makes tea, then y is playing tennis can be inferred via the universal biconditional elimination rule. For all y, if y plays tennis, then y is making tea can be inferred via the universal biconditional elimination rule.