What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Mary is a taxi driver or Charles is writing a letter. If Mary were a taxi driver, then Charles is rich. For all z_1, z_1 will write a letter if and only if z_1 is rich.
If Charles plays tennis, then Mary is a taxi driver. For all z_1, if z_1 writes a letter, then z_1 is rich. For all z_1, if z_1 were rich, then z_1 is writing a letter.