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: There is at least one y for which if y drives a car, then y is climbing a mountain. For all y, y will not drive a car. For all y, if y climbs a mountain, then y is driving a car. For all y, y will climb a mountain if and only if y will drink water.
For all y, y will not climb a mountain can be inferred via the universal modus tollens rule. There is at least one y for which y will drive a car if and only if y will climb a mountain can be inferred via the existential biconditional introduction rule. There is at least one y for which y will climb a mountain if and only if y will drive a car can be inferred via the existential biconditional introduction rule. For all y, if y climbs a mountain, then y is drinking water can be inferred via the universal biconditional elimination rule. For all y, if y drinks water, then y is climbing a mountain can be inferred via the universal biconditional elimination rule.