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, if x_10 were a janitor, then x_10 is a cashier. For all x_10, if x_10 were a janitor, then x_10 is sad. For all x_10, if x_10 were sad, then x_10 is a janitor. For all x_10, if x_10 were a cashier, then x_10 is sad.
For all x_10, if x_10 were a janitor, then x_10 is sad can be inferred via the universal transitivity rule. For all x_10, if x_10 were sad, then x_10 is a cashier can be inferred via the universal transitivity rule. For all x_10, if x_10 were a cashier, then x_10 is a janitor can be inferred via the universal transitivity rule. For all x_10, x_10 is a janitor if and only if x_10 is sad can be inferred via the universal biconditional introduction rule. For all x_10, x_10 is sad if and only if x_10 is a janitor can be inferred via the universal biconditional introduction rule.