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: For all y_1, y_1 will not work. For all y_1, if y_1 climbs a mountain, then y_1 is working. For all y_1, y_1 will climb a mountain if and only if y_1 will work. If it is cold, then William is climbing a mountain.
For all y_1, y_1 will not climb a mountain can be inferred via the universal modus tollens rule. For all y_1, if y_1 climbs a mountain, then y_1 is working can be inferred via the universal biconditional elimination rule. For all y_1, if y_1 works, then y_1 is climbing a mountain can be inferred via the universal biconditional elimination rule. For all y_1, y_1 will not climb a mountain can be inferred via the universal biconditional elimination rule.