What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y, if y were an astronaut, then y is an artist. For all y, if y were an artist, then y is an astronaut.
For all y, y is an astronaut if and only if y is an artist. For all y, y is an artist if and only if y is an astronaut.