What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? William is rich if and only if Patricia is fast. Robert is not a cashier. If William were rich, then Mary is a poet. Robert is a cashier if and only if Mary is a poet.
If William were rich, then Patricia is fast. If Robert were a cashier, then Mary is a poet. If Patricia were fast, then William is rich. If Mary were a poet, then Robert is a cashier. Mary is not a poet.