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