What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? John is drinking water. For all x_17, if x_17 writes a letter, then x_17 is a janitor. Elisabeth is a janitor if and only if Jessica is a cashier. For all x_17, if x_17 were a janitor, then x_17 is writing a letter. Jessica is not a cashier.
John is drinking water and Jessica is not a cashier. Jessica is not a cashier and John is drinking water. If Elisabeth were a janitor, then Jessica is a cashier. If Jessica were a cashier, then Elisabeth is a janitor. Elisabeth is not a janitor. For all x_17, x_17 will write a letter if and only if x_17 is a janitor. For all x_17, x_17 is a janitor if and only if x_17 will write a letter.