What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one x_12 for which if x_12 writes a letter, then x_12 is fast. For all x_12, x_12 is an office clerk or x_12 will write a letter. For all x_12, x_12 is an office clerk if and only if x_12 will play tennis. For all x_12, x_12 is fast if and only if x_12 will play tennis.
For all x_12, if x_12 were an office clerk, then x_12 is playing tennis. For all x_12, if x_12 were fast, then x_12 is playing tennis. For all x_12, if x_12 plays tennis, then x_12 is an office clerk. For all x_12, if x_12 plays tennis, then x_12 is fast.