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: There is at least one x_13 for which x_13 will work if and only if x_13 is an office clerk. For all x_13, x_13 will not work. For all x_13, if x_13 were happy, then x_13 is an office clerk.
There is at least one x_13 for which if x_13 works, then x_13 is an office clerk can be inferred via the existential biconditional elimination rule. There is at least one x_13 for which if x_13 were an office clerk, then x_13 is working can be inferred via the existential biconditional elimination rule. There is at least one x_13 for which x_13 is not an office clerk can be inferred via the existential biconditional elimination rule.