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_3 for which x_3 is sad if and only if x_3 is fast. For all x_3, x_3 is fast if and only if x_3 is sad.
For all x_3, if x_3 were fast, then x_3 is sad. There is at least one x_3 for which if x_3 were sad, then x_3 is fast. For all x_3, if x_3 were sad, then x_3 is fast. There is at least one x_3 for which if x_3 were fast, then x_3 is sad.