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_8, x_8 is a writer or x_8 is an electrician. For all x_8, x_8 is an electrician if and only if x_8 is sad. There is at least one x_8 for which x_8 is not a writer or x_8 will go running. For all x_8, if x_8 were sad, then x_8 is a doctor. For all x_8, x_8 is not a doctor.
For all x_8, x_8 is not sad can be inferred via the universal modus tollens rule. There is at least one x_8 for which x_8 is an electrician or x_8 will go running can be inferred via the existential resolution rule. For all x_8, if x_8 were an electrician, then x_8 is sad can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 were sad, then x_8 is an electrician can be inferred via the universal biconditional elimination rule.