What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x, x is sad if and only if x will play tennis. For all x, x is not sad. For all x, if x were sad, then x is playing tennis.
For all x, if x were sad, then x is playing tennis. For all x, if x plays tennis, then x is sad. For all x, x will not play tennis.