What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_23, x_23 will write a letter if and only if x_23 is a poet. Joseph is a lawyer if and only if Sarah is writing a letter. Joseph is not a lawyer.
If Joseph were a lawyer, then Sarah is writing a letter. If Sarah writes a letter, then Joseph is a lawyer. Sarah is not writing a letter. For all x_23, if x_23 writes a letter, then x_23 is a poet. For all x_23, if x_23 were a poet, then x_23 is writing a letter.