What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Thomas were a server, then David is drinking water. If Thomas were a server, then it is sunny. If it is sunny, then David is drinking water. If David drinks water, then Thomas is a server.
If Thomas were a server, then David is drinking water. If it is sunny, then Thomas is a server. If David drinks water, then it is sunny. Thomas is a server if and only if David is drinking water. David is drinking water if and only if Thomas is a server.