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: If Robert were a mechanic, then Robert is happy. For all x, x is happy if and only if x is a mechanic.
For all x, if x were happy, then x is a mechanic can be inferred via the universal biconditional elimination rule. For all x, if x were a mechanic, then x is happy can be inferred via the universal biconditional elimination rule.