What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all x_4, if x_4 were an astronaut, then x_4 is a soldier. For all x_4, x_4 is an electrician or x_4 is a nurse. For all x_4, if x_4 were a nurse, then x_4 is a soldier. For all x_4, if x_4 plays squash, then x_4 is an astronaut. There is at least one x_4 for which x_4 is not an electrician or x_4 will play squash.
For all x_4, if x_4 plays squash, then x_4 is a soldier can be inferred via the universal transitivity rule. There is at least one x_4 for which x_4 is a nurse or x_4 will play squash can be inferred via the existential resolution rule.