What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z_1, z_1 is a carpenter if and only if z_1 is rich. If David were a carpenter, then David is rich.
For all z_1, if z_1 were a carpenter, then z_1 is rich. For all z_1, if z_1 were rich, then z_1 is a carpenter.