What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: James is not sad. Richard is a bartender if and only if David is playing squash. If Richard were a bartender, then William is a doctor. William is a doctor if and only if James is sad.
If Richard were a bartender, then David is playing squash can be inferred via the biconditional elimination rule. If William were a doctor, then James is sad can be inferred via the biconditional elimination rule. If David plays squash, then Richard is a bartender can be inferred via the biconditional elimination rule. If James were sad, then William is a doctor can be inferred via the biconditional elimination rule. William is not a doctor can be inferred via the biconditional elimination rule.