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 x_9 for which if x_9 drives a car, then x_9 is climbing a mountain. For all x_9, x_9 will drive a car if and only if x_9 is happy. For all x_9, x_9 is happy or x_9 is a writer. For all x_9, x_9 will not climb a mountain.
There is at least one x_9 for which x_9 will not drive a car can be inferred via the existential modus tollens rule. For all x_9, if x_9 drives a car, then x_9 is happy can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 were happy, then x_9 is driving a car can be inferred via the universal biconditional elimination rule.