What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z, z will not write a letter. For all z, z will climb a mountain or z will not write a letter. For all z, z will write a letter or z will not climb a mountain.
For all z, if z writes a letter, then z is climbing a mountain. For all z, if z climbs a mountain, then z is writing a letter.