What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_15, if x_15 were a lawyer, then x_15 is a nurse. Thomas is a nurse if and only if William is taking a plane. Richard is an office clerk if and only if Thomas is a lawyer. William is not taking a plane.
If Thomas were a nurse, then William is taking a plane. If Richard were an office clerk, then Thomas is a lawyer. If William takes a plane, then Thomas is a nurse. If Thomas were a lawyer, then Richard is an office clerk. Thomas is not a nurse.