What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Mary takes a plane, then Mary is a mechanic. If Mary were a mechanic, then Patricia is excited. For all x_12, x_12 is not a mechanic. If Patricia were excited, then Mary is taking a plane.
If Mary were a mechanic, then Mary is taking a plane. If Patricia were excited, then Mary is a mechanic.