What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z_4, if z_4 were a carpenter, then z_4 is writing a letter. There is at least one z_4 for which if z_4 writes a letter, then z_4 is not a janitor. For all z_4, z_4 is a janitor.
There is at least one z_4 for which z_4 will not write a letter.