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 were curious, then x_6 is an office clerk. For all x_6, if x_6 were an office clerk, then x_6 is curious. For all x_6, if x_6 were an office clerk, then x_6 is writing a letter. There is at least one x_6 for which if x_6 were a bartender, then x_6 is curious. For all x_6, x_6 will not write a letter.
For all x_6, x_6 is not an office clerk can be inferred via the universal modus tollens rule. For all x_6, if x_6 were curious, then x_6 is writing a letter can be inferred via the universal transitivity rule. There is at least one x_6 for which if x_6 were a bartender, then x_6 is an office clerk can be inferred via the existential transitivity rule. For all x_6, x_6 is curious if and only if x_6 is an office clerk can be inferred via the universal biconditional introduction rule. For all x_6, x_6 is an office clerk if and only if x_6 is curious can be inferred via the universal biconditional introduction rule.