What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? David is sleeping if and only if Karen is climbing a mountain. If David sleeps, then Joseph is not a mechanic. Joseph is a mechanic. If it is sunny, then Karen is climbing a mountain.
David is not sleeping. If David sleeps, then Karen is climbing a mountain. If Karen climbs a mountain, then David is sleeping.