What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Mary is a janitor if and only if Jennifer is driving a car. Mary is an astronaut if and only if it is overcast. If Mary were a janitor, then it is overcast. Mary is not an astronaut.
If Mary were a janitor, then Jennifer is driving a car. If Mary were an astronaut, then it is overcast. If Jennifer drives a car, then Mary is a janitor. If it is overcast, then Mary is an astronaut. It is not overcast.