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, if x_10 plays tennis, then x_10 is climbing a mountain. There is at least one x_10 for which x_10 will write a letter if and only if x_10 will play tennis. For all x_10, if x_10 climbs a mountain, then x_10 is playing tennis.
For all x_10, x_10 will play tennis if and only if x_10 will climb a mountain. For all x_10, x_10 will climb a mountain if and only if x_10 will play tennis. There is at least one x_10 for which if x_10 writes a letter, then x_10 is playing tennis. There is at least one x_10 for which if x_10 plays tennis, then x_10 is writing a letter.