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: Robert is working if and only if it is cold. Robert is not working. For all x_23, x_23 is not happy. Mary is playing tennis if and only if Michael is happy.
If Robert works, then it is cold can be inferred via the biconditional elimination rule. If Mary plays tennis, then Michael is happy can be inferred via the biconditional elimination rule. If it is cold, then Robert is working can be inferred via the biconditional elimination rule. If Michael were happy, then Mary is playing tennis can be inferred via the biconditional elimination rule. It is not cold can be inferred via the biconditional elimination rule.