What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? William is not fast. For all x_20, x_20 will cook and x_20 will take a plane. Robert is a taxi driver if and only if William is fast.
If Robert were a taxi driver, then William is fast. If William were fast, then Robert is a taxi driver. Robert is not a taxi driver. For all x_20, x_20 will cook. For all x_20, x_20 will take a plane.