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 write a letter if and only if z will make tea. For all z, if z makes tea, then z is a doctor. For all z, if z were a doctor, then z is writing a letter.
For all z, if z makes tea, then z is writing a letter. For all z, if z writes a letter, then z is making tea. For all z, if z makes tea, then z is writing a letter.