What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z_1, if z_1 were an office clerk, then z_1 is not playing squash. For all z_1, if z_1 were a writer, then z_1 is an artist. For all z_1, z_1 is an office clerk if and only if z_1 is an artist. There is at least one z_1 for which z_1 will play squash. For all z_1, z_1 is a writer if and only if z_1 is an artist.
There is at least one z_1 for which z_1 is not an office clerk. For all z_1, if z_1 were an office clerk, then z_1 is an artist. For all z_1, if z_1 were a writer, then z_1 is an artist. For all z_1, if z_1 were an artist, then z_1 is an office clerk. For all z_1, if z_1 were an artist, then z_1 is a writer.