What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_13, if x_13 cooks, then x_13 is an office clerk. David is not an astronaut. For all x_13, if x_13 were an office clerk, then x_13 is cooking. David is an astronaut if and only if William is cooking.
If David were an astronaut, then William is cooking. If William cooks, then David is an astronaut. William is not cooking. For all x_13, x_13 will cook if and only if x_13 is an office clerk. For all x_13, x_13 is an office clerk if and only if x_13 will cook.