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: William is a nurse. David is a scientist if and only if it is late. If William were a nurse, then David is a scientist.
David is a scientist can be inferred via the modus ponens rule. If David were a scientist, then it is late can be inferred via the biconditional elimination rule. If it is late, then David is a scientist can be inferred via the biconditional elimination rule.