What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If David writes a letter, then Linda is playing tennis. It is not windy. If Linda plays tennis, then David is writing a letter. It is windy if and only if David is writing a letter.
David is writing a letter if and only if Linda is playing tennis. Linda is playing tennis if and only if David is writing a letter. If it is windy, then David is writing a letter. If David writes a letter, then it is windy. David is not writing a letter.