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_6, if x_6 works, then x_6 is an office clerk. For all x_6, x_6 will drive a car or x_6 will work. For all x_6, if x_6 drives a car, then x_6 is an office clerk. There is at least one x_6 for which if x_6 were an office clerk, then x_6 is working.
There is at least one x_6 for which if x_6 drives a car, then x_6 is working can be inferred via the existential transitivity rule. For all x_6, x_6 is an office clerk can be inferred via the universal disjunction elimination rule. There is at least one x_6 for which x_6 is an office clerk if and only if x_6 will work can be inferred via the existential biconditional introduction rule. There is at least one x_6 for which x_6 will work if and only if x_6 is an office clerk can be inferred via the existential biconditional introduction rule.