What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_10, x_10 is a cashier. For all x_10, x_10 will play tennis or x_10 is a sailor. For all x_10, x_10 is a sailor if and only if x_10 will write a letter. For all x_10, if x_10 plays tennis, then x_10 is writing a letter.
For all x_10, if x_10 were a sailor, then x_10 is writing a letter. For all x_10, if x_10 writes a letter, then x_10 is a sailor.