What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Mary were a writer, then William is taking a plane. If William takes a plane, then Linda is playing squash. Mary is a writer if and only if Linda is playing squash.
If Mary were a writer, then Linda is playing squash. If Mary were a writer, then Linda is playing squash. If Linda plays squash, then Mary is a writer.