What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Sarah is not taking a plane. If it is sunny, then Mary is reading a book. If Mary reads a book, then Linda is writing a letter. If Elisabeth were not a mechanic, then it is sunny. Sarah is taking a plane if and only if Elisabeth is a mechanic.
If it is sunny, then Linda is writing a letter. If Elisabeth were not a mechanic, then Mary is reading a book. If Sarah takes a plane, then Elisabeth is a mechanic. If Elisabeth were a mechanic, then Sarah is taking a plane. Elisabeth is not a mechanic.