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_10, x_10 is a janitor if and only if x_10 is curious. For all x_10, if x_10 were curious, then x_10 is writing a letter. There is at least one x_10 for which if x_10 were a janitor, then x_10 is an artist. For all x_10, if x_10 were an artist, then x_10 is a janitor. For all x_10, x_10 will not write a letter.
For all x_10, x_10 is not curious can be inferred via the universal modus tollens rule. There is at least one x_10 for which x_10 is a janitor if and only if x_10 is an artist can be inferred via the existential biconditional introduction rule. There is at least one x_10 for which x_10 is an artist if and only if x_10 is a janitor can be inferred via the existential biconditional introduction rule. For all x_10, if x_10 were a janitor, then x_10 is curious can be inferred via the universal biconditional elimination rule. For all x_10, if x_10 were curious, then x_10 is a janitor can be inferred via the universal biconditional elimination rule.