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 drink water if and only if z will write a letter. For all z, z will drink water or z is not fast. There is at least one z for which z will write a letter or z is fast.
For all z, if z were fast, then z is drinking water. For all z, if z drinks water, then z is writing a letter. For all z, if z writes a letter, then z is drinking water.